- Magna Carter (1215) suggested that people had some control over what a monarch does and certain rights.
- Certain texts and commentaries such as Bagehot's "The English Constitution".
- One of the major sources due to power of Parliament to make and change constitution. Major statutes (Acts of Parliament) eg. Wales Act 1998 set up Welsh National Assembly, Scotland Act 1998, Human Rights Act 1998, House of Lords Act 1999.
- Prerogative powers of the Crown - certain powers expected to be carried out by a monarch but many have since been passed on to ministers to act in the monarch's name (e.g. to declare war, make treaties and give honours.)
- Laws and customs of Parliament - certain procedures…