This is the 87th Biggles book to be published. The book was originally published by Brockhampton Press in September 1966. As with all of the later Biggles books it is an Air Police adventure where Biggles and his cohorts are based at Scotland Yard in London under Air Commodore Raymond, although as normal this does not stop them chasing around the world after criminals.
As the title to the book suggests, Biggles is on the hunt for some international gun runners. Quoting from the wrapper front flap gives us a flavour. "Biggles advertises his Services in the hope that he can pick up the trail of a gun-running racket which is causing international concern. The Mysterious character of the Count who answers his advertisement, and the suspiciously high salary he offers, suggests to Biggles that he might be on to something big. When he is shot down, Biggles decides that the Sudd - 400 miles of mud and water - is no place for a picnic, let alone a big commercial airliner."