In the OM foyer at RAF Valley, a glass-topped cabinet held the Visitors Book, signed only by VIPs. The pages would be turned at various intervals to show who had visited.
One day, the page in view read 'Philip' (yes, that one) and underneath 'To all my mates on XXX course'.
It was there for a few days until the PMC spotted it. Outraged, he summoned the course leader and demanded an explanation, pointing at the Visitors Book with fury.
"Oh, sorry sir - let me fix it" said the course leader. Whereupon he opened the cabinet, ripped out the offending page and tore it up. Needless to say, the PMC went into low Earth orbit at this piece of vandalism. Then he notice that the rest of the course were killing themselves with laughter - the offending page had actually been a carefully planted Xerox copy of the real one with Phil-the-Greek's signature and had been skilfully inserted.
The PMC failed to appreciate the joke - I gather a few course members 'volunteered' for extra Orderly Officer duty as a result.