The Webley Self-Loading Pistol was an up-and-coming design in early magazine-fed pistols. The gun was designed in 1910 by the Webley & Scott company. The Mk. 1 entered police service in 1911 in a .38 ACP model for the London Metropolitan Police. The .455 version was adopted by the Royal Navy in 1912 as the first automatic pistol in British service. The pistol was also adopted by the Royal Horse Artillery and the Royal Flying Corps . Its predecessor was the unsuccessful Mars Automatic Pistol, made around 1900.