[...] I should thank him for his 15 years service [...]
Aargh - not that sycophantic "Thank you for service" platitude which seems to have made its way across the Atlantic these days.
A quick look at web links of his indicate rank Flt Lt, Pilot Training 72-76 and then RAF Provost branch 76 to career end. Uni 65-68
Quite reasonable - a few holds were quite common during training back then. At White Waltham we had a chap who was at the AEF downstairs flying space cadets whilst holding for an OCU; as a break from Chipmunking, now and again he would nip off to do some Hunter refresher flying. You could easily drag pilot training out to 4 years only to be chopped at Chiv - and prefer a branch change rather than becoming a nav because in 1976 you might be lucky to be offered ME pilot training only if you'd made it to an OCU! There was a glut of ME pilots at the time and the worthless Jetstreams went into storage for a while, although some refresher training was flown on the Beech Baron at Bournemouth.
I was at Valley in 1975 when some chap came into the bar only to be recognised by people who'd been on the same Officer Training course - but had later become a Provost officer. "Hello, mate - what are you doing in this neck of the woods?" he was asked. "Err, oh I'm visiting a friend in OMQs" or somesuch excuse was the reply.
Actually, probably nothing of the sort. This was at exactly the time when Alistair Steadman, an ex-Vulcan captain who lived on Anglesey, was arrested for trying to sell secrets to the Russians. Convicted, he served 9 years behind bars!