Jefferis developed the idea of the squash head further. His most ambitious project was a bomb designed to sink capital ships, his ideas were put forward by himself and Lord Cherwell in 1944 and coincided with the Admiralty's interest in developing a homing bomb for use against the Japanese. The development of this weapon was supported by the Air Staff and MAP who allocated it a higher priority that any other anti-capital ship weapon. When the war ended, development of the 'Cherwell-Jefferis' bomb was continued under the code names "Journey's End" and "Blue Boar".