A series of very compact submachine guns - possibly better described as personal defense weapons - was made in Britain at the end of World War Two under the name Viper (as an interesting aside, snake names were popular - the EM-1 and EM-2 were code-named Cobra and Mamba during the same timeframe). The first was a simplified take on the Sten, but the No.3 Viper here is a wholly new gun made from the ground up. Designed to hang under the arm and be used either with or without the detachable shoulder stock, it is chambered for standard 9x19mm ammunition. Oddly, the No.3 Viper uses MP40 magazines, instead of what should have been ubiquitous Sten magazines.

According to Matthew Moss at The Armourer's Bench, the project was organized by a Mr. Oliphant of the Ministry of Supply, and the design team included Derek Hutton-Williams (later to be superintendent of the Royal Small Arms Factory, Enfield and the director general of Britain’s Royal Ordnance Factories) and Messrs. J. Soutcott and W. T. Walker.

Many thanks to the Royal Armouries for allowing me to film this tremendously rare artifact! The NFC collection there - perhaps the best military small arms collection in Western Europe - is available by appointment to researchers.