It's a Northernerism - Double Hard Bastard
"We don't ave guns oop north!"
"Now sod off ya southern fairy!"
- its suggesting as "Northern Monkeys" we lack the knowhow to weild a gun due to gun crime being more prominent in the south UK, yet we are prehistoric enough to put the bullets in you through caveman power.
Or you should stop...
I'm not even gonna say it!