HR
Rock Apes is a term of endearment for the RAF Regiment.
Monkeys are the RMP or perhaps they were the CMP (they changed from Corps to Royal in 1945) when you knew them. The origin of both terms is not known but one explanation for the RMP being called Monkey's is that by lore, the day the baboons leave the Rock of Gibraltar, it will no longer be British. To ensure this never happens, in days of old, it was the job of the Provost Sergeant to feed them so they would stay. It seems to have worked up to now but nobody reckoned on President Blair and his policy of European appeasment.
Another explanation is during the days of a conscript Army, CMP/RMP of a robust nature were needed to control unruly soldiers. These men were not the sharpest tools in the box and henceforth were known as Monkeys because of their intelect.
Personally, I prefer the first explanation.