ALL Metropolitan Police officers in uniform are required to have their identifying letters and numbers on display at all times. The regulation was last renewed in the force's "Dress Code Policy" in 2005 but is a long-standing convention which goes back to the earliest days of Victorian policing.

The policy says: "Where provided, epaulettes with identifying letters and numerals or insignia of rank must be worn and must be correct and visible at all times." Although not specified, breach of any official police policy can make officers subject to disciplinary proceedings.

The "shoulder numbers" worn by all constables and sergeants carry two pieces of information.

There is a two-letter code which shows which borough the officers are from. Tactical support group officers only have the letter U and other specialist units have their own letters.

The numbers give the officers' warrant numbers.

All sergeants have one or two digits and all constables have three. Officers with four digits are volunteer special constables or Police Community Support Officers.

Higher ranks from inspector above do not show their number, only the insignia of their rank, with inspectors having two pips.

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