On 10 November 1935 a resident of Wimpole Street called the local Welbeck telephone exchange to report a fire that had broken out in the house opposite. This was the established way of seeking the emergency services, but there was no way of prioritising such calls since they used the same exchange number as all other calls. Consequently the caller was unable to raise the alarm, and five women died in the fire.
A letter from the frustrated neighbour appeared in The Times shortly afterwards, and this brought the issue to national attention. On 10 December the Postmaster General, who was responsible for the telephone network, informed parliament that he was to launch an inquiry into what he referred to as ‘urgency calls’.
The 999 service was launched in London on 30 June 1937, and initially covered a 12 mile radius from Oxford Street. The number was initially chosen because it was easy to modify existing payphones, which used rotary dials, to allow the number 9 to connect without money needing to be inserted. 111 was ruled out since the accidental touching of telephone wires could accidentally trigger the call.
The first verified 999 call that led to an arrest took place a week after the service began operating, when a burglar was apprehended following a call from a member of the public to the police. Within a short space of time the system consistently proved to be a success, and its popularity and effectiveness in London led to the introduction of a 999 service in Glasgow the following year. It reached other British cities after the Second World War, but only expanded to cover the whole of the UK in 1976.