For more than three hours, on a freezing February night, the 12 men from the Special Air Service had been lying behind a low, threadbare bit of hedge on the edge of a rural chapel car park near the Northern Irish village of Clonoe.

According to intelligence reports, this was where the East Tyrone Brigade of the Irish Republican Army were going to assemble the largest and deadliest weapon in the IRA’s very considerable armoury and mount it on the back of an open lorry.

At which point, the SAS would jump out and apprehend the gun and the terrorists red-handed before they could set off to reduce their intended target – the local police station – to Swiss cheese.

For this was not just any old machine gun. Firing more than 600 armour-piercing 12.7mm rounds per minute, the Russian-made DshK (known as the ‘Dushka’) can stop a plane or armoured vehicle at a range of more than a mile.

Just one problem. At 10.40pm, the SAS realised that the intelligence they had received was not entirely accurate. Yes, the target was Coalisland police station.