In the run up to World War Two Ralph founded a company to market and build air raid shelters "of the strong kind". The enterprise was variously known as the Bomb & Gas Proof Shelter Co., National Bomb & Gas Proof Shelters Ltd., and British Air-Raid Shelters Ltd.

The venture seems to have been a complete failure. At a bankruptcy court hearing in March 1941, Hancock admitted that he knew very little about building underground. Adding that it had cost the company £1500 to waterproof a shelter once it had been completed. The company folded just as war was declared in September 1939. 

 Publicity Booklet for the Bomb Shelter Company