In May 2004 a gang of armed robbers were moments away from getting their hands on £33 million worth of gold bullion and cash, which would have been one of the biggest hauls in British criminal history. They had conned their way through security at Heathrow and entered the Swissport cargo depot.

However, rather than confronting a group of terrified employees, they were met by a welcoming committee of Flying Squad officers, who had been tipped off about the raid.

A baggage handler who had been arrested in a smaller operation had, in the language of the Flying Squad, “rolled over”.

He is now in the Witness Protection Scheme and has a new identity after giving evidence against nine people who were involved in the raid.

The gang members were sentenced to a total of 76 years by Kingston Crown Court.

The success of that operation led to the rejuvenation of cultivating supergrasses - a system that had been seen as uncoordinated, unreliable and unaccountable in the late 1970s and early 1980s.

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