Selection: Authorised Firearms Officers (AFOs) are selected by the chief constable of each force. Selection is based on the Association of Chief Police Officers' "Manual of Guidance on the Police Use of Firearms". The Home Office is considering, w ith the ACPO, improving the selection criteria of armed officers. Attitude, maturity and calmness are as important as marksmanship. "Glory seekers" are excluded, as are loners and officers with alcohol or domestic problems. The final selection is made by an officer of ACPO rank.

Rules of engagement: AFOs are taught to give immediate warnings that they are armed and to tell suspects to drop their weapons and surrender. They are trained to fire at the upper body and never to fire at or from a moving car, not to fire where a memberof the public's life would be endangered and not to use arms within 24 hours of drinking alcohol.

The Call to Arms: 1983: Stephen Waldorf, a television technician, shot when police mistook him for David Martin, an armed robber.

1985: Cherry Groce shot and crippled by police who entered her home in Brixton, south London. This and the Waldorf shooting prompted a major examination of the way armed officers were deployed.

July 1991: The Metropolitan Police introduced armed response vehicle (ARV) teams, small groups of highly trained marksmen to be deployed anywhere in the capital at short notice and intended to replace a larger pool of less well trained AFOs.

February 1994: murders of PC Patrick Dunne and Sgt Derek Robertson.

March 1994: PC Simon Carroll and PC Jim Seymour shot in Brixton, south London.

May 1994: the Metropolitan Police announced that ARV officers would be allowed to wear their Smith & Wesson .38 handguns openly when called to most types of incident. Previously needed authority of high ranking officer to remove guns from a secure metal box in the vehicle. Metropolitan Police Commissioner Paul Condon said he hoped the move would "postpone the necessity to routinely arm police officers". Other AFOs continue to need the authorisation of a senior officer for the issue of firearms.

July 1994: James Sharples, outgoing chairman of the ACPO's firearms committee, warned that routine armed patrols of inner-city trouble spots "could come sooner rather than later". Chief constables recommended allowing more junior ranks to authorise the issue of firearms in emergencies.

September 1994: 180 officers in rapid response units in Manchester allowed to wear their guns openly.