The New Protean gear, described in this patent, had nearly all the attributes of the fork derailleurs that dominated that 1930s - and what’s more it appears that it worked quite well.

But that’s a funky half-moon shaped chain.

• Publisher: UK Intellectual Property Office
• Inventor: Charles Montague Linley
• Country: UK
• Date: UK application filed September 1899
• Derailleur brands: Whippet
• Derailleurs: Whippet