In The Case of the Flying Clown, Wing Commander Jimmy Strickland was a British security agent who had been sent to work undercover in "Air Thrills Unlimited", an international air circus whose main financial backer was the war-mongering industrialist Jacob Ironmaster.
Strickland, a personal friend of Biggles, was an ex-R.A.F. officer who performed stunt flying during the annual R.A.F. displays. U.S. and British security authorities had become suspicious of the activities of the newly formed "Air Thrills Unlimited" circus. When the circus advertised for a stunt pilot, British security sent in Strickland. Not long thereafter, Strickland died in an aircrash. At first it was assumed that this was an accident. However, a British mechanic, Jones, left the circus and reported to Air Commodore Raymond his belief that Strickland's aircraft had been sabotaged. He also related Strickland's last words: "Tell them to stop Nemo in Paris."