I first heard that one in '72 when, as a very green Sapper, I was on a fuel pipeline exercise in Suffolk getting AVTUR from an RFA tanker lying off Orford Ness to the USAF bases at RAF Woodbridge and Bentwaters. The nearest pub was the Oyster in Butley, a mile or so down the road from where we were camped and every Sunday was a superb song session!