'We've put a bomb in the sports club. It's set to go off in 20 minutes': Moment ... trends now

It was a scene that looked more at home in a police drama.

Two men were filmed carrying a bomb into a car before a red-haired woman calmly drove it to its destination as music played in the background.

Moments earlier, she had given a warning to authorities, telling them from a phone box: 'We've just put a bomb in the Queen's University Sports Club. It is set to go off in 20 minutes.'  

The 1972 bombing was just one shocking moment captured by an American documentary team led by academic J Bowyer Bell.

Bell's footage also showed the moment of the explosion, which left several people hurt.

His documentary was lost for decades after being aired only fleetingly upon its release, but has now been revealed in new BBC 4 programme The Secret Army after reporter Darragh MacIntyre tracked down some of those involved in making it.

Bell's documentary, also called The Secret Army, was made with permission from the IRA's most senior figures.

Irish broadcaster Tim Pat Coogan says in the programme, which aired last week: 'These seasoned guerillas, who relied so much on secrecy, went before the cameras and, you know, in effect, put their heads on the block.' 

The criminals behind several attacks were shown without masks.

The documentary also captured secret IRA training classes for recruits, attempts to shoot down helicopters in Derry, and a meeting in Belfast led by Seamus Twomey, who later became the organisation's chief of staff.

The IRA allowed Bell to make the programme in the belief that 1972 would be their 'year of victory'. 

They hoped that the film would act as propaganda and win more funds from American sympathisers.