With a value of £1,250, a tank that can hold 10 litres of water and a firing range of 40ft, it is said to be the world's most sophisticated machine gun water pistol.

Engineer Alex Bygrave, 27, of Streatham Hill, south London, spent 50 hours designing and building the first-ever Gatling-style water pistol from scratch - using 55 separate parts from everyday life.