Hmm, a quick Google turned up
this from the oldcranwellians which shows a Peter Maitland graduating from Cranwell as part of C Sqdn of 76 entry in 1959. I guess he could have been a Flt Lt 4 years later. Interestingly, it also shows that 76 Entry included one M J Graydon who, of course went on to be CAS (I knew him as OC 11 Sqdn in the late 1970's). The page also shows that Peter Maitland died of natural causes in 2013. At the time in question (60 - 63) 80 Sqdn were flying Canberras out of Bruggen so it is conceivable that he went to another UK based Canberra Sqdn in 1963.
A check of the FreeBMD website shows 2 Peter J Maitlands born between 1935 & 1940 (a speculative date range based on a likely age at graduation), one in Epping and one in Gosport. There is one marriage for a Peter J Maitland, in 1969 in Alton which is, of course, not a million miles away from both Gosport and RAF Odiham. (There are other entries for Peter Maitlands btw)
I also turned up a news story from Feb 1961 to the effect that a Fg Off Peter Maitland, son of AVM Maitland of East Harptree, had just completed a winter survival course in the Bavarian Alps.
None of which, of course is definitively linked to the pewter tankard nor does it show where his surviving family may be today but may be of help in taking the search forward. Another idea might be to put an ad in Air Mail, the magazine of the RAF Association, and see if that turns anything up. Service careers, especially at officer ranks tend to run in families so there may be a surviving Maitland still around and reading Air Mail.
I hope that the tankard can be reunited with a rightful owner.
