Early one July morning in 1941 a Belgian farmer encountered a curious object among his crops: a cylinder a couple of feet long with a parachute attached.

Through a gap in one side he could just about make out a pair of beady eyes staring back at him. Attached was a note. It was from British Intelligence and asking for help.

Inside was a pigeon, codenamed NURP 39 TTTI. The lettering stood for the National Union of Racing Pigeons and number 39 denoted the year it fledged.

But this was not just any pigeon. Rather a bird which would end up proving so important it would deliver a message which ended up being passed all the way to Winston Churchill.