A very brave bloke who sat for hours in the rear gun turret of a WW2 bomber having the shit
shot out of him by enemy fighters. It was lonely freezingly cold job with a high mortality rate.
A WW2 bomber had several defensive gun turrets, the rear one was the most vunerable to being hit by an enemy fighter's machine guns.
Section of the River Cam behind the Cambridge University Colleges where punting takes place.
"Lets take a picnic and bottle in a punt out on the backs"
The cannon balls on a man o' war were stacked and held in place by a brass ring on the deck known as a brass monkey
. In cold weather the sea spray would turn to ice thus freezing the cannon balls together and onto the ring.
Hence the expression "It's cold enough to freeze balls on a brass monkey
" or simply "brass monkey weather
". Note that the correct phrase is "on" NOT "off" a "brass monkey
". The expression is often corrupted to hint at an association with a man's testicles balls