Constitutional conventions
The nutshell
A constitutional convention is an unwritten rule about how the country should be run. It is not a law that a court can enforce, but the people in charge almost always follow it.
Every fact on this page comes from official guides to the UK constitution and non-partisan explainers. Each source tag — like Parl — opens where a fact comes from.
The basics
What a constitutional convention is
A constitutional convention is an unwritten rule about how the country should be run. UK Parliament describes a convention as an understanding about how something should be done that, although not a law, is almost always followed.Parl
Not a law, but almost always kept
A convention is not written in an Act of Parliament, so no court can enforce it. Even so, the people in charge almost always keep to it. UK Parliament describes a convention as not legally enforceable, but almost universally observed.Parl
Some examples
By convention, the King asks the person most likely to have the support of the House of Commons to become Prime Minister. By another convention, called the Sewel convention, the UK Parliament does not normally make laws on matters handed to Scotland, Wales or Northern Ireland without the consent of the devolved parliament or assembly. The UCL Constitution Unit sets out both.CU
Where conventions are written down
Some conventions have been written down in official guides. The Institute for Government notes that many were set out in the Cabinet Manual, first published in 2011, which lists the rules and conventions for running the government.IfG The House of Commons Library adds that writing a convention into such a guide does not turn it into a law.HoC
- A convention is an unwritten understanding about how something should be done, and although it is not legally enforceable it is almost universally observed, the UK Parliament glossary states
- Conventions are one of the sources of the UK constitution, alongside statute law, common law and practice, the House of Commons Library records
- Some conventions have been set out in official guides, such as the Cabinet Manual first published in 2011, the Institute for Government notes
- A convention is not a law a court can enforce — the UK Parliament glossary describes conventions as not legally enforceable, though almost always observed
- A convention is not written down in one place — the House of Commons Library records that the UK constitution has never been codified into a single document
- Writing a convention into a guide does not turn it into law — the Institute for Government notes the Cabinet Manual is a guide to convention, not a codified constitution
The deep end6 min
Where conventions fit in the UK constitution
The UK does not have its constitution written down in a single document. The House of Commons Library records that the constitution is built from common law, statute law, conventions and practice, and that conventions are one of its sources.HoCUK Parliament describes a convention as an unwritten understanding about how something should be done that, although not legally enforceable, is almost universally observed.Parl
Why a convention is not a law
A convention works differently from an Act of Parliament. UK Parliament sets out that a convention is not legally enforceable, so no court will punish anyone for breaking it.Parl The UCL Constitution Unit describes conventions as rules of good political behaviour, held in place by political pressure rather than by the courts, and able to change over time.CU
Conventions written into official guides
In recent decades some conventions have been set out in official documents. The Institute for Government notes that the Cabinet Manual, first published in 2011, gathered the rules, conventions and procedures for the operation of government into one guide, including the convention of collective cabinet responsibility.IfG The House of Commons Library records that guides like the Cabinet Manual and the Ministerial Code are not legally binding, so writing a convention down does not make it a law.HoC
Two worked examples
The UCL Constitution Unit gives two clear examples. First, by convention the King appoints as Prime Minister the person most likely to command the confidence of the House of Commons, rather than choosing freely.CU Second, the Sewel convention holds that the Westminster Parliament does not normally legislate on matters handed to Scotland, Wales or Northern Ireland without the consent of the devolved legislature.CU