Constitutional conventions of the United Kingdom
While the United Kingdom does not have a codified constitution that is contained within a single document, the collection of legal instruments that have developed into a body of law known as constitutional law has existed for hundreds of years. As part of this uncodified British constitution, constitutional conventions play a key role. Some rules that are observed by the various constituted parts though they are not written in any document having legal authority; there are often underlying enforcing principles that are themselves uncodified. Nonetheless it is very unlikely that there would be a  departure of such conventions without good reason, even if an underlying enforcing principle has been overtaken by history, as these conventions also acquire the force of custom. Conventions are often thought of as "unwritten" but sometimes conventions are recorded in writing e.g. the Cabinet Manual, the Ministerial Code. Similarly conventions are often thought of as evolving over time but they can sometimes be created at a specific moment in time e.g. the Salisbury Convention. Examples include: