While I was stationed with the RAF Police at RAF Marham in Norfolk in 1983, the conversation one day in the Sergeant's Mess centred around the subject of practical jokes.
One of the firemen who I was talking to, asked if I knew about the foam making compound trick. I hadn't, and he went on to explain. “The foam,” he said, “used by the airport fire tenders is created when two separate powder compounds are brought together in water.” “So, how does that help me,” I replied. “Well,” he said, “If one powder is placed in the toilet bowl and the other placed in the water storage tank, whoever flushes the toilet will get more than they bargained for.” “Brilliant,” I said, “When can I have some?” “Later that afternoon,” was the answer.
At the time, my Flight Sergeant, a Scotsman who I'll call Hamish to protect his real identity, had a sense of humour and I thought it was about time we played a joke on him
The opportunity came a few weeks later when I had the opportunity to hatch a plan. Luckily, there were two toilet facilities in our police control complex; one for the troops and one for the management and operations room staff. The compounds were duly added to the 'Management toilet' during the quiet hours of the night shift, when Hamish had gone out to check on his troops.
The area was then placed 'out of bounds' to everyone else
Hamish was always pretty regular in his ablutions and we knew he would visit the toilet sometime before going off duty. We waited patiently, but the hours seemed to drag by without so much as a movement from Hamish.
We were beginning to give up, when suddenly we saw him disappear in the direction of the toilet with his newspaper. Quickly and quietly, we all gathered outside the door to await the inevitable. Again, it seemed like ages before we heard the cistern being flushed.
Initially, nothing happened but then suddenly there was a loud shriek as Hamish, overcome by a sudden build up of foul smelling foam, tried to work out what the hell was happening around him. However, I think he quickly worked it out as he heard us all laughing at the door.
At this point, I decided to make myself scarce for a while
When I did go back some time later, the cubicle was completely enveloped in foam. Apparently, I had gone a little over-board on the amounts required. Luckily, Hamish saw the funny side of the prank, but it took us ages to clean up the mess....!!