Quoted from British Built Aircraft by Ron Smith: "The Willoughby Delta was a two-seat, twin-engine, twin-tail boom design with a fixed undercarriage, powered by two 125 hp Menasco engines and registered
G-AFPX. The name Delta reflects the tapered triangular fairing between the outer wing panels and the tail booms. The crew sat in a pod at the wing center section.

The design, although unconventional in appearence, was backed up by careful wind tunnel testing, and was intended to be a sub-scale demonstrator for a larger transport aircraft. G-AFPX was constructed at Minster Lovell between Witney and Burford, and first flew in April 1939 at Witney, demonstrating remarkable good performance. Unfortunately, the prototype was destroyed in a fatal accident on July 10, 1939, and no further development took place.

The Willoughby Delta Co. Ltd, which developed the machine, had registered offices in Moorgate, London."