The UK does not have an equivalent of the FBI. Most criminal
investigations are handled by the Police, and the most serious ones
are dealt with by the London Metropolitan Police (aka Scotland
Yard). Serious Organised crime is dealt with by the Serious
Organised Crime Agency (SOCA), a government organisation. Secret
investigations are done by the Security Service, better known as
MI5 (Military Intelligence Section Five). Both the Police, SOCA and
MI5 come under control of the Home Office, an executive department
of the British Government.