Notes · PoliticsUK · A-Levels

The British Constitution

The UK constitution is uncodified, unentrenched and unitary, resting on the twin pillars of parliamentary sovereignty and the rule of law and drawn from five distinct sources rather than a single document. This topic examines its nature and sources, the wave of reform since 1997, and the central evaluative debates - whether the constitution should be codified and where sovereignty now lies.

5 sections~21 min reading time3 competenciesLevel Foundation 1 · Standard 2 · Advanced 2

T·0111 / 18

Exam profile

AO1 · Demonstrate knowledge and understanding of the nature and sources of the UK constitution and of reform since 1997AO2 · Analyse how the sources interrelate and how reform has redistributed political powerAO3 · Evaluate whether the UK should adopt a codified constitution and where sovereignty now lies, reaching a substantiated judgement

Operators:explain and analyseevaluateto what extentanalyse and evaluate this statementexamine

basic level

AS-Level expects the nature and sources of the constitution and the main reforms since 1997.

higher level

The full A-Level requires sustained evaluation of codification and of the location of sovereignty after devolution and Brexit, reaching a judgement.

Depth

Text

Contents · 5 sections

The British Constitution

The nature of the UK constitution#

FoundationAQA 7152/1 Section A: The nature and sources of the British constitutionDfE GCE Politics subject content

Codified versus uncodified constitutions

Fig. 1Both types define the powers of the state and the citizen's relationship to it; they differ in form, entrenchment and flexibility.

A constitution is the set of rules that establishes the composition, powers and functions of the institutions of the state, regulates the relationships between them, and defines the relationship between the state and the individual. The UK's constitution is distinctive because it is uncodified - its rules are not gathered into a single, authoritative document but are dispersed across statutes, judicial rulings, conventions and works of authority. This is often loosely called an 'unwritten' constitution, but that label is misleading: most of it (statute law, case law) is very much written down; it is simply not codified into one document. The classic contrast is with the United States, whose 1787 Constitution is codified, entrenched and self-consciously supreme.

Three further features define the UK constitution and each carries analytical weight. First, it is unentrenched: because there is no higher constitutional law, any part of the constitution can be changed by an ordinary Act of Parliament passed by a simple majority, exactly as any other law is - there is no special amendment procedure and no supermajority. Second, it is unitary (though now better described as 'quasi-federal' after devolution): sovereignty is concentrated in a single central authority, the Westminster Parliament, from which all other bodies derive their powers. Third, it rests on the flexibility this produces - the constitution can evolve continuously in response to circumstance, without the rigidity of a codified document.

The constitution is underpinned by two fundamental principles that the constitutional theorist A.V. Dicey called its 'twin pillars'. The first is parliamentary sovereignty: Parliament is the supreme legal authority, able to make or unmake any law; no Parliament can bind its successors; and no body - not even a court - can override or set aside an Act of Parliament. The second is the rule of law: the principle that everyone, including the government, is subject to and equal before the law, that no one may be punished except for a proven breach of the law, and that the law is applied through fair and independent courts. There is a latent tension between the two pillars - an all-powerful Parliament could in theory legislate to breach the rule of law - which the courts and conventions manage in practice.

The character of the constitution also flows from its historical development. Unlike the constitutions born of revolution, independence or defeat (the USA, France, Germany), the UK's constitution was never created at a single 'constitutional moment'; it has evolved gradually and organically over centuries, accreting through landmark settlements such as Magna Carta and the 1689 Bill of Rights rather than being designed as a whole. This evolutionary quality is the root of both its celebrated flexibility and the central criticism made of it - that it is unclear, uncertain and offers weak protection against an over-mighty executive that controls a sovereign Parliament.

Worked example

Distinguishing 'uncodified' from 'unwritten'

Explain why it is more accurate to describe the UK constitution as 'uncodified' rather than 'unwritten'.

Define codified
A codified constitution gathers the constitution's rules into a single, authoritative, entrenched document (the US Constitution).
Identify the UK's written elements
Much of the UK constitution IS written down - statutes (the Parliament Acts, the Human Rights Act), and thousands of pages of case law - just not in one document.
Identify the unwritten elements
Some of it is genuinely unwritten: conventions such as collective ministerial responsibility exist only as understood practices.
Draw the distinction
'Unwritten' implies nothing is recorded, which is false; 'uncodified' accurately captures that the rules exist but are dispersed across sources rather than gathered and entrenched.

Result: The UK constitution is best called 'uncodified': its rules are mostly written but are scattered across statute, common law, conventions and works of authority rather than assembled into one supreme document.

Typical mistakes

Calling the UK constitution 'unwritten' - most of it is written (statute, case law); the accurate term is 'uncodified'.
Confusing parliamentary sovereignty (the legal supremacy of Parliament) with the rule of law (equality before the law) - or ignoring the tension between them.

Active revision

Explain and analyse three features of the UK constitution. (9 marks)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for politics (Department for Education)

The sources of the constitution#

StandardAQA 7152/1 Section A: The nature and sources of the British constitutionDfE GCE Politics subject content

The five sources of the UK constitution

Fig. 2The uncodified constitution is drawn from five sources; statute law is supreme because Parliament is sovereign.

Because the UK constitution is uncodified, its rules must be located across five distinct sources, and a strong answer can define each and give an example. The first and most important is statute law - Acts of Parliament. Because Parliament is sovereign, statute is the highest source: where a statute conflicts with any other source it prevails. Constitutionally significant statutes include the Parliament Acts 1911 and 1949 (limiting the Lords), the Human Rights Act 1998, the Scotland Act 1998 and the Constitutional Reform Act 2005. Statute is the means by which almost all deliberate constitutional reform is enacted.

The second source is common law - the body of law developed by judges through their decisions and through legal principles established over centuries, including the residual royal prerogative powers exercised by ministers. Landmark rulings and long-standing common-law principles (such as the presumption of individual liberty, or the rules of natural justice) form part of the constitution. Common law is subordinate to statute - Parliament can always override a judicial decision by legislating - but it fills the gaps and interprets the meaning of statute.

The third source is conventions - the unwritten rules and customs of political practice that are followed because of their long usage and accepted authority, even though they are not legally enforceable. Conventions are the 'oil' of the constitution: the monarch grants Royal Assent to bills, the government resigns or seeks a dissolution if it loses the confidence of the Commons, the Salisbury Convention restrains the Lords from blocking manifesto commitments, and collective ministerial responsibility binds the Cabinet. Their strength - flexibility - is also their weakness: because they are not legally binding they can be broken or disputed, and their uncertain status is a key argument for codification.

The fourth source is works of authority - respected constitutional texts written by experts that, while not legally binding, are treated as authoritative guides to how the constitution operates. The best-known are Walter Bagehot's The English Constitution (1867), A.V. Dicey's Introduction to the Study of the Law of the Constitution (1885) and Erskine May's parliamentary practice (the 'bible' of Commons procedure). The fifth source is treaties and international agreements - historically, the European Communities Act 1972 incorporated European Community/EU law, giving it effect (and, via Factortame, supremacy) in the UK until the European Union (Withdrawal) Act 2018 and withdrawal in 2020 removed it. Understanding how these five sources rank - statute at the top, conventions and works of authority carrying only practical, not legal, force - is essential to explaining how an uncodified constitution actually works.

Worked example

Ranking a conflict between sources

A convention and a new Act of Parliament point in opposite directions. Which prevails, and why?

Identify the sources
A convention is a non-legal customary rule; an Act of Parliament is statute law.
Apply the ranking
Statute is the supreme source because Parliament is sovereign; conventions carry only customary, not legal, force.
Resolve
The statute prevails and is legally enforceable; the convention is displaced (Parliament can legislate contrary to any convention).
Evaluate
This shows why conventions are a weak protection - they depend on being observed and can be overridden or abandoned, an argument used for codification.

Result: The Act of Parliament prevails, because statute is the supreme source under parliamentary sovereignty; the episode illustrates the fragility of conventions and the case for codifying the constitution.

Typical mistakes

Treating conventions as legally binding - they are not enforceable in court; their authority is customary and practical.
Forgetting that statute overrides all other sources, so that common law and conventions can always be displaced by an Act of Parliament.

Active revision

Explain and analyse three sources of the UK constitution. (9 marks)

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Politics (7152) specification (AQA)

Constitutional reform since 1997#

StandardAQA 7152/1 Section A: The nature and sources of the British constitutionDfE GCE Politics subject content

Constitutional landmarks and reform

Fig. 3The constitution has evolved by accretion; the period since 1997 marks an unusually concentrated burst of deliberate reform.

The election of the Labour government in 1997 opened the most sustained programme of constitutional reform in modern British history, driven by a diagnosis that power was over-centralised, rights were weakly protected and institutions were undemocratic. The reforms fall into recognisable clusters, and a strong answer groups them rather than listing them randomly. The first cluster is the decentralisation of power: devolution to Scotland (the Scotland Act 1998), Wales (the Government of Wales Act 1998) and Northern Ireland (following the Good Friday Agreement 1998), plus an elected Mayor and Assembly for London. Devolution transferred substantial powers away from Westminster and is the single most far-reaching change, moving the UK towards a quasi-federal arrangement.

The second cluster is the strengthening of rights. The Human Rights Act 1998 incorporated the European Convention on Human Rights into UK law, allowing individuals to enforce Convention rights in domestic courts and requiring public bodies to act compatibly with them - though, to preserve parliamentary sovereignty, the courts may only issue a 'declaration of incompatibility' rather than strike down an Act. The Freedom of Information Act 2000 gave a right of access to information held by public bodies, and the Equality Act 2010 consolidated anti-discrimination law. Together these gave citizens clearer, more enforceable protections than the old reliance on residual common-law liberties.

The third cluster is the modernisation of institutions and the judiciary. The House of Lords Act 1999 removed all but 92 of the hereditary peers, making the second chamber more legitimate though still wholly unelected. The Constitutional Reform Act 2005 created a UK Supreme Court (operational 2009), separating the highest court from the House of Lords, and reformed the office of Lord Chancellor - a deliberate strengthening of the separation of powers and of judicial independence. Electoral reform introduced proportional and mixed systems for the devolved bodies and other elections, though not for Westminster.

Reform continued under later governments, showing this is not a purely 'Labour' story. The Fixed-term Parliaments Act 2011 (a Coalition measure) removed the Prime Minister's prerogative power to time elections by fixing five-year terms - only for it to be repealed by the Dissolution and Calling of Parliament Act 2022, which restored the prerogative, a striking illustration of the constitution's flexibility and reversibility. Further devolution followed (the Scotland Acts 2012 and 2016, the Wales Acts 2014 and 2017), and Brexit removed EU law as a source of the constitution. Evaluating the reform programme means asking whether it went far enough (critics note the unelected Lords, the retention of FPTP for Westminster, the absence of a codified constitution and an entrenched bill of rights) or created new problems (the West Lothian question, tensions in the Union) - and the strongest answers reach a judgement rather than merely cataloguing the changes.

Worked example

Grouping the reforms for an essay

Organise the post-1997 reforms into analytical clusters for a 25-mark essay.

Decentralisation
Devolution to Scotland, Wales, Northern Ireland and London - power dispersed away from Westminster (quasi-federalism).
Rights
Human Rights Act 1998, Freedom of Information Act 2000, Equality Act 2010 - clearer, enforceable protections.
Institutions and judiciary
House of Lords Act 1999, Constitutional Reform Act 2005 (Supreme Court) - stronger separation of powers and judicial independence.
Electoral and executive
Proportional/mixed systems for devolved bodies; Fixed-term Parliaments Act 2011 (repealed 2022) - a reversible constraint on the executive.
Judge the balance
Significant dispersal of power and stronger rights, but the Lords remain unelected, Westminster keeps FPTP, and there is still no codified constitution - 'significant but incomplete'.

Result: Clustering the reforms into decentralisation, rights, institutions/judiciary and electoral/executive shows a genuinely significant redistribution of power and strengthening of rights, while the unelected Lords, FPTP and the absence of codification support the judgement that reform remains incomplete.

Typical mistakes

Presenting reform as entirely a 1997-2010 Labour project - the Coalition (Fixed-term Parliaments Act) and later governments (2022 repeal, further devolution, Brexit) continued it.
Listing reforms without analysing their effect on the location of power or evaluating whether they went far enough.

Active revision

Evaluate the view that constitutional reform since 1997 has been significant but incomplete. (25 marks)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for politics (Department for Education)

Should the UK adopt a codified constitution?#

AdvancedAQA 7152/1 Section A: The nature and sources of the British constitutionDfE GCE Politics subject content

The case for and against codification

Fig. 4The codification debate is a trade-off between certainty and protection of rights and flexibility and democratic accountability.

The debate over codification is one of the classic 25-mark essays, and the strongest answers set it up as a genuine contest of principles before reaching a judgement. The case for codification rests first on clarity and accessibility: a single, authoritative document would state the fundamental rules clearly, so that citizens, officials and courts could know with certainty what the constitution requires - ending the reliance on vague, disputed conventions. A codified constitution would be entrenched, protected by a special amendment procedure, which supporters argue would safeguard fundamental rights and the structure of government against an over-mighty executive that currently needs only a simple parliamentary majority to change the constitution.

The case for codification continues with the argument about the executive and rights. Because the UK constitution is unentrenched and Parliament is sovereign, and because the government usually controls a Commons majority, critics argue the executive faces too few constitutional limits - Lord Hailsham's phrase 'elective dictatorship' captures the fear. A codified, entrenched constitution with an enforceable bill of rights would create a higher law that even a majority government could not override, and would give the judiciary the power to strike down unconstitutional action - a stronger check than the current declaration of incompatibility. Supporters add that almost every other democracy manages with a codified constitution, and that the UK's arrangements look increasingly anomalous.

The case against codification is equally principled and, in the exam, must be given full weight. The central argument is flexibility: the uncodified constitution can evolve continuously and adapt to new circumstances without the cumbersome amendment procedures that make codified constitutions rigid - the ease with which devolution or the Human Rights Act was enacted (and the Fixed-term Parliaments Act repealed) is cited as a virtue, not a defect. Opponents argue that entrenchment transfers power from elected, accountable politicians to unelected judges, who would have to interpret the document and could strike down the decisions of a democratic Parliament - a 'juristocracy' that is itself undemocratic. They also warn that codification would freeze a particular set of arrangements at one moment, and that the process of drafting and agreeing a document would be fraught and divisive.

Reaching a judgement is what separates the top band from the middle. A sophisticated answer recognises that the debate turns on a trade-off between certainty and protection of rights on the one hand, and flexibility and democratic accountability on the other, and that where one stands depends on how much one fears executive over-reach versus judicial over-reach. A defensible judgement might be that the strongest case is not for full codification but for targeted entrenchment (for example, of key rights or of the devolution settlements), which would address the worst weaknesses - the vulnerability of rights and of the Union to a bare majority - while preserving much of the flexibility the system's defenders value. The essential skill is to argue a clear line to a conclusion, not to leave the two sides balanced.

Worked example

Model essay plan: should the UK codify its constitution?

Plan a 25-mark answer evaluating the view that the UK should adopt a codified constitution.

Introduction and thesis
Define codification and entrenchment; signal a judgement - that the strongest case is for targeted entrenchment rather than full codification. Set up the trade-off.
The case for
Clarity and certainty replace disputed conventions; an entrenched bill of rights protects liberties against a bare majority; it limits the executive ('elective dictatorship').
The case against
Flexibility lets the constitution evolve (devolution, HRA, FTPA repeal); entrenchment transfers power to unelected judges; democratic accountability is preferable to juristocracy.
Weigh the two
The debate turns on whether executive over-reach or judicial over-reach is the greater danger; certainty and protected rights are weighed against flexibility and accountability.
Judgement
Conclude that targeted entrenchment (of key rights and the devolution settlements) captures the main benefits while preserving most of the flexibility - a stronger position than either full codification or the status quo.

Result: A top-band plan frames codification as a trade-off between certainty and protected rights and flexibility and accountability, gives full weight to both sides, and argues a clear line to a substantiated judgement - here, that targeted entrenchment is preferable to either full codification or the present arrangements.

Typical mistakes

Producing a balanced list of pros and cons with no judgement - the 25-mark bands reward a sustained line of argument to a conclusion.
Assuming codification would automatically improve democracy, ignoring the counter-argument that it transfers power to unelected judges.

Active revision

'The UK should adopt a codified constitution.' Analyse and evaluate this statement. (25 marks)

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for politics (Department for Education)

Where does sovereignty now lie?#

AdvancedAQA 7152/1 Section A: The nature and sources of the British constitutionDfE GCE Politics subject content

Legal versus political sovereignty

Fig. 5Legal sovereignty remains with Parliament; political sovereignty is dispersed - the two have diverged.

Sovereignty means ultimate, supreme authority, and answering where it lies requires the crucial distinction between legal sovereignty and political sovereignty. Legal sovereignty is the supreme law-making authority recognised by the courts; in the UK this rests, by the doctrine of parliamentary sovereignty, with the Westminster Parliament (the Crown-in-Parliament). Political sovereignty is where power actually lies in practice - the ability to determine outcomes - which may diverge from the legal position. Keeping the two apart is the key to a sophisticated answer, because many developments have eroded political sovereignty while leaving legal sovereignty formally intact.

Several developments have appeared to challenge parliamentary sovereignty, and each must be assessed carefully. Devolution transferred wide powers to the Scottish Parliament, the Senedd and the Northern Ireland Assembly, and the Sewel Convention holds that Westminster will not normally legislate on devolved matters without consent; politically it is now very hard for Westminster to reclaim these powers, yet legally it retains the sovereign right to do so (devolution is statutory, and Parliament could amend or repeal the devolution Acts). EU membership had a more direct effect: the European Communities Act 1972 gave EU law effect in the UK and, in the Factortame case, the courts disapplied an Act of Parliament that conflicted with EU law - a genuine, if voluntary and reversible, limitation on legal sovereignty.

Brexit is the decisive recent event for this debate and can be argued both ways. On one reading, withdrawal restored parliamentary sovereignty in full: the European Communities Act was repealed, EU law ceased to be supreme, and the ability of Parliament to make or unmake any law without an external constraint was recovered - the reversibility of the 1972 arrangement proving that sovereignty had only ever been 'pooled', not surrendered. On another reading, the referendums that decided EU membership (1975 and 2016), Scottish independence (2014) and other questions have entrenched a new source of political authority - popular sovereignty - so that on fundamental constitutional questions it is now politically very difficult for Parliament to act against a clear referendum result, whatever its legal power.

The judiciary and the Human Rights Act add a final layer. The courts cannot strike down an Act of Parliament, so legal sovereignty is preserved; but the growth of judicial review and the declaration of incompatibility mean the courts exert real influence over government, and some scholars argue the traditional Diceyan doctrine has softened into a more contested, 'bi-polar' sovereignty shared between Parliament and the courts. The best judgement recognises that legal sovereignty formally remains with Parliament - reaffirmed by Brexit - but that political sovereignty is now widely dispersed among the devolved bodies, the electorate acting through referendums, the courts and (until 2020) the EU, so that the simple Diceyan picture of an all-powerful Westminster Parliament is legally accurate but politically misleading.

Worked example

Arguing Brexit both ways on sovereignty

Assess whether Brexit restored parliamentary sovereignty or entrenched popular sovereignty.

Restoration argument
Repeal of the European Communities Act ended the supremacy of EU law (reversing Factortame); Parliament recovered the unfettered power to make or unmake any law - legal sovereignty restored.
Popular-sovereignty argument
The decision was taken by referendum; a clear popular vote is now politically near-binding on fundamental constitutional questions, entrenching the electorate as a rival source of authority.
Distinguish the two sovereignties
Legally, sovereignty returned in full to Parliament; politically, the referendum route has created an expectation that the people decide constitutional fundamentals.
Judgement
Both are true at different levels: Brexit restored LEGAL parliamentary sovereignty while strengthening the POLITICAL authority of referendums - confirming that the two have diverged.

Result: Brexit restored parliamentary sovereignty in the legal sense (the ECA was repealed and EU-law supremacy ended) while reinforcing popular/referendum sovereignty in the political sense - so the honest judgement is that it did both, at different levels of sovereignty.

Typical mistakes

Conflating legal and political sovereignty, and so concluding either that Parliament is all-powerful or that it has none - the point is that the two have diverged.
Treating devolution or referendums as legal limits on sovereignty; they constrain Parliament politically, but legally it retains the sovereign power to legislate.

Active revision

Evaluate the view that parliamentary sovereignty is now more myth than reality. (25 marks)

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Politics (7152) specification (AQA)

References & sources

Sources

Department for Education

GCE AS and A level subject content for politics

AQA

AQA AS and A-level Politics (7152) specification

The British Constitution

5 sections~21 min reading time3 competenciesLevel Foundation 1 · Standard 2 · Advanced 2

The British Constitution

Key points

Distinguishing 'uncodified' from 'unwritten'

Key points

Ranking a conflict between sources

Key points

Grouping the reforms for an essay

Key points

Model essay plan: should the UK codify its constitution?

Key points

Arguing Brexit both ways on sovereignty

Sources

The British Constitution

Key points

Distinguishing 'uncodified' from 'unwritten'

Key points

Ranking a conflict between sources

Key points

Grouping the reforms for an essay

Key points

Model essay plan: should the UK codify its constitution?

Key points

Arguing Brexit both ways on sovereignty

Sources