In English law, the black cap was worn by a judge when passing a sentence of death. Although it is called a “cap”, it is not made to fit the head like a typical cap does; instead it is a simple plain square made of black fabric. When worn, it is placed on the head on top of the judicial wig, with one of the four corners of the black fabric facing outward.
The death penalty has now been abolished in England and Wales, but the black cap is still part of a judge’s official regalia, and as such it is still carried into the High Court by each sitting judge. It is worn every year on 9 November when the new Lord Mayor of the City of London is presented to the Law Courts.