The Crime Investigation Department (CID) is the branch of all Territorial police force

Territorial police force

The phrase Territorial Police Force varies in precise meaning according to the country to which it is related, generally distinguishing a force whose area of responsibility is defined by sub-national boundaries from others which deal with the entire country or a restricted range of...

s within the British Police

Policing in the United Kingdom

Law enforcement in the United Kingdom is organised separately in each of the legal systems of the United Kingdom: England & Wales, Northern Ireland and Scotland ....

 and many other Commonwealth

Commonwealth of Nations

The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...

 police forces, to which plain clothes detective

Detective

A detective is an investigator, either a member of a police agency or a private person. The latter may be known as private investigators or "private eyes"...

s belong. It is thus distinct from the Uniformed Branch and the Special Branch

Special Branch

Special Branch is a label customarily used to identify units responsible for matters of national security in British and Commonwealth police forces, as well as in the Royal Thai Police...

.

The Metropolitan Police Service

Metropolitan Police Service

The Metropolitan Police Service is the territorial police force responsible for Greater London, excluding the "square mile" of the City of London which is the responsibility of the City of London Police...

 CID, the first such organisation, was set up on 7 April 1878 by C. E. Howard Vincent

C. E. Howard Vincent

Colonel Sir Charles Edward Howard Vincent KCMG CB DL , known as Howard Vincent or C. E. Howard Vincent, was a British soldier, barrister, police official and Conservative Party politician who sat in the House of Commons from 1885 to 1908.-Early life and education:Vincent was born in Slinfold, near...

. Originally, it was under the direct command of the Home Secretary

Home Secretary

The Secretary of State for the Home Department, commonly known as the Home Secretary, is the minister in charge of the Home Office of the United Kingdom, and one of the country's four Great Offices of State...

, but since 1888 has been under the authority of the Commissioner

Commissioner of Police of the Metropolis

The Commissioner of Police of the Metropolis is the head of London's Metropolitan Police Service, classing the holder as a chief police officer...

.
CID officers are required to have had at least two years as a uniformed officer before applying to transfer to the branch and receive further training when they do so.