Just been rereading this very entertaining thread.
Having been on detachment there in 1991, I mainly flew the Puma by night with the 100 gallon ferry tank permanently fitted in the cabin and normally filled right up; we seldom carried more than one passenger in addition to the kit we carried (those who know will understand).
One evening we landed at last light at one of the FOBs, having completed one job (I can’t recall which base it was) and needed refuelling to maximum asap and a crew briefing for a further urgent task. The TSW chap said he was happy to refuel by himself and so we three crew went off to brief. We came back after the briefing to find fuel everywhere and the TSW chap almost in tears and similarly soaked in fuel at the side of the aircraft, leaning on the fuel cap!
The ferry tank had been used to feed the mains on the previous flight. Due to a crew error, (no names mentioned but he was a navigator), the tap on the tank hadn’t been closed after it had drained. The TSW chap unfortunately decided off his own bat to fill the ferry tank first, which wasn’t usual. He therefore inadvertently filled the mains via the ferry tank opening! When he opened the mains cap, the main tank was already bulging full and it blew back at him, with a head of a good metre of Jet fuel above him. He couldn’t get the cap back on fully due to the pressure, so he had to stand holding it on, like the Dutch boy with his finger in the dyke, until we returned about fifteen minutes later. I turned off the ferry tap and we got the cap back on. We sent the TSW chap (who thankfully wasn’t injured, apart from severe loss of composure) off to drain his wellies and get himself sorted. We all stank of jet fuel for the rest of the night.