The reality isn’t much sillier than your suggestions! He was the Silver Stick, a bodyguard to QEII!At some point hasn’t APB had a formal role as a Courtier?
Polisher of the Regal Swizzlestick?
Grand Marshall of the Balmoral Spurtle?
Maybe he’s on the Courtier bench as a sub in case a Courtier takes a tumble arse over gold-braided tit?
(Plus a whole long list of other army/royalish posts - he earns his invite regardless of Cam!)