The Great Panjandrum was a massive wheel-like device, about 10 feet in diameter, designed to roll across beaches, smash through sea walls, and deliver a 4,000-pound explosive charge into enemy fortifications. Cordite rockets attached around the circumference of two wooden wheels would propel it forward at 60 mph.
Testing on the beaches of Devon was catastrophically entertaining. During trials at Westward Ho!, the rockets fired unevenly, causing the device to veer wildly off course. In one famous test, it turned in circles, shed rockets that chased observers along the beach, and charged toward a group of high-ranking officials and cameramen who scattered in terror. A dog cheerfully chasing the device added to the chaos.
The device was never used in combat. Some historians speculate that the intentionally conspicuous and absurd beach tests were actually part of Operation Fortitude's deception campaign—designed to be observed by German spies and convince them the Allies were developing beach-assault equipment for use at Pas-de-Calais.