Candidates are required to gain approval from their superiors before embarking on a series of interviews, psychological and physical fitness tests, medical examinations and assessment days, before permission to commence firearms training is given.The common role of an SFO is to assault premises involved in a siege situation, effect high-risk firearms related arrests and respond to terrorist threats.[8][10][11][19] The national Combined Response Firearms Teams established for the Olympics was maintained after the closing of the Games forming the basis of the CTSFO Network.[20][11] In 2013, West Midlands Police CTSFOs deployed to London to support the MPS following the Murder of Lee Rigby in Operation Pegboard.[24] When working at airports, nuclear sites, on protection duties and deployed in armed response vehicles in certain areas, 'standing authority' is granted to carry personal sidearms.[25] All members of the Police Service of Northern Ireland have authority to carry a personal issue handgun as a matter of routine, both on duty and off.[26] United Kingdom law allows the use of "reasonable force" in order to make an arrest or prevent a crime[27][28] or to defend oneself.[35][36] However this does not include the Police Service of Northern Ireland where all roughly 7,000 officers there are trained to AFO as standard and carry a Glock 17 sidearm as routine.
Authorised firearms officers standing guard at the entrance to Downing Street, London, home of the UK Prime Minister. This officer is attached to the
Diplomatic Protection Group
.