The painting 'Light and Colour' had been hidden for eight years

Turner's masterpieces "Light and Colour" and "Shade and Darkness", on loan from the Tate, were snatched from the wall of the Kunsthalle Shchirn gallery in Frankfurt in 1994.

A leading figure in Frankfurt's Balkan mafia was believed to be the brains behind the theft, but only two of the actual thieves were arrested at the time.

By the end of 2002 both paintings had been recovered, but only after the Tate had paid several million pounds to a well-placed intermediary.

The film reveals how two retired Metropolitan policemen and a German solicitor helped the Tate secure the return of two of Britain's national treasures.

Did the Tate pull off a remarkable rescue, paying only for information that would lead them to the paintings' whereabouts?

Or have they in effect paid a ransom and set a dangerous precedent that makes future art theft more likely?

Underworld Art Deal was broadcast on Wednesday, 9 November, 2005 at 1900 GMT on BBC Two.