Did he buy it from Lillywhite's? They made a chuffing fortune flogging mail order Webley revolvers to well-heeled young chaps in the trenches during Round One, and that looks like their kind of upmarket packaging
Nope. The site I linked as source says the weapon was presented to his Late Majesty , KGVI in his capacity as an officer in that new-fangled Home Guard.
I doubt WSC ordered the Thompson he was pictured with via the Sears catalogue either.
And as to packaging for a bit of good ol' PR - I take it you never saw the gold plated SMG on the Royal Ordnance stand at the British Army Equipment Exhibition in the late 80s either ?
I believe they sold a few to the usual blinged-up Middle Eastern crew.