Does the UK have a constitution?
Yes — it is simply not written in a single document, which is what people mean when they say it is unwritten. The rules exist; they are just scattered, and some of them are not law at all.
Where the constitution actually lives:
Statute. Acts of Parliament of constitutional significance — those establishing devolution, human rights, the relationship between the Houses, electoral law and the independence of the judiciary.
Common law, developed through court judgments, including fundamental principles such as the rule of law and access to justice.
Constitutional conventions, which are binding by practice rather than by law. That the monarch grants assent to bills, that a government resigns when it loses confidence, and that ministers are accountable to Parliament are conventions — followed consistently and not enforceable in court.
Works of authority, treatises historically treated as settling points where no other source does.
International treaties and their domestic effect.
Parliamentary rules and practice, governing procedure.
The central principle: parliamentary sovereignty. Parliament can make or unmake any law, and no Parliament can bind its successor. This is the foundational difference from codified systems — there is no higher law against which legislation can be struck down, and courts interpret rather than override.
The arguments for it. Flexibility, allowing evolution without formal amendment; and an absence of rigid entrenchment that can freeze outdated arrangements.
The arguments against. Conventions depend on restraint, so a government willing to disregard them faces limited legal constraint; the boundaries are contested; rights are more easily altered than in codified systems; and most citizens cannot readily find out what the rules are, which is a genuine democratic problem.
Why it has become a live issue. Recent decades have seen repeated disputes over prorogation, the scope of judicial review, the status of devolution settlements, and the relationship between ministers and civil servants — all of which turn on conventions and contested interpretation rather than on clear text.
Other uncodified systems exist, including New Zealand and Israel.
General information.