This is the earlier of the two BSA derailleur patents that I have been able to find. It dates from before D-day, a time when post war peace cannot have seemed to be guaranteed, and it describes a derailleur that, I believe, was never produced.

One of the inventors, William Charles Urry, has an unusual surname and may be related to Francis John Urry, a noted writer on cycling, who (possibly) received an MBE for services to cycling.

• Publisher: UK Intellectual Property Office
• Inventor: William Charles Urry, Victor Ernest Needham and The Birmingham Small Arms Company Ltd.
• Country: UK
• Date: UK application filed January 1944
• Derailleur brands: BSA
• Derailleurs: unknown model