Islands and the Isle of Man, which are not parts of the British sovereign territory) use the same general system, but often have fewer senior ranks. Chief constable is the title of the head of each United Kingdom territorial police force except the Metropolitan Police and City of London Police, which are headed by commissioners. Ranks above chief superintendent are usually non-operational management roles, and are often referred to as "chief officer" ranks, but the longer phrase "chief police officer" or similar in legislation is specifically a commissioner or chief constable, a "senior police officer" being their immediate deputy. The Commissioner of the Metropolitan Police is often considered to be the highest police rank within the United Kingdom, although in reality every chief constable and the two commissioners are supreme over their own forces and are not answerable to any other officer. Epaulettes are normally black with white sewn on or silver metal insignia, although high-visibility uniforms are often yellow with black insignia. Epaulette insignia Uniform insignia The rank of an officer can be found in varying details of the uniform such as headgear, sleeve patches and tunic collar details. Insignia on hats and uniforms can vary between forces within the UK and the following tables below will not accurately represent all constabularies within the UK. British Transport Police As a variation to the standard set, the deputy chief constable of the British Transport Police wears two rows of oak leaves on their hat. Northern Ireland The Police Service of Northern Ireland (PSNI) adopted the same rank system as elsewhere in the United Kingdom on 1 June 1970, but has a different version of the rank insignia, with the star from the PSNI badge replacing the crown. Unusually, the star is worn below the pip by chief superintendents and by the chief constable, who wears both symbols above his tipstaves. The PSNI has retained the RUC's distinctive inverted (point-up) sergeants' chevrons, worn on the lower sleeve in formal uniform. PSNI officers do not wear the custodian helmet and female officers wear a different hat from other forces. The PSNI rank structure and epaulette insignia is the same as the territorial police in Great Britain, except that the crown is replaced with the design from the PSNI badge and sergeants' chevrons are point up. In addition to the epaulettes being a green colour rather than a black, this is to match