Developed originally as the AT-100 4x2 Internal Security Vehicle in 1971, the AT-104 was introduced the following year as the first vehicle specifically designed as a response to the urban insurgency in Northern Ireland, a wave of violence, known as "The Troubles" began in the summer of 1969 and ended in 2001. In this time, the Irish Republican Army split into the Marxist influence "Official IRA" and the violent, sectarian "Provisional IRA", eventually killing 497 civilians, 638 British soldiers, 271 police officers of the Royal Ulster Constabulary, and 276 IRA members.
The impetus for the development of the AT-104 was the retirement of the FV 1611 Humber "Pig", and armored car with decades of service, sent to be scrapped in the mid to late 60's. However, rather than buy new vehicles, the British military instead recalled 500 Humbers to active duty, shipping them off to be uparmored one by one. In the end, only 30 AT-104s were ever sold; 24 to the Brunei military and another 6 to a special unit of the Dutch State Police. The AT-104 is the immediate predecessor of the AT-105 Saxon, a major armored personnel carrier for the British military during and after the Cold War.