One of my colleagues was ex-BRIXMIS and would occasionally have us rolling about in hysterics with some of his tales...
On concerned the time when the spooks had provided him with a device with which to measure the thickness of armour on some new Sovietski tanksi - they were instructed to press it against the armour, press the button and take a reading... So one dark night on tour they found one and crept up to it and pressed the button as briefed...
But what they spooks hadn't told him was that the device used some sonic technique. As they pressed the button, there was an almighty and quite deafening 'BOING' which echoed through the night, so they bravely rushed into hiding. A few seconds later, the hatch flew open and some poor Soviet grunt appeared with his hands over his ears, who then peered around his tank wondering what the hell had caused the noise which had so rudely interrupted his slumbers. My colleague said that the hardest part was trying to stifle their laughter.
I know that chap! Another funny aspect to his story was that he had a very common name and was posted to BRIXMIS because he was on his record of service, a fluent Russian speaker. However, there was another chap with the same name and rank who was the real Russian speaker and sometime in the past, they had got confused.