The engine of this extraordinary motorcycle is the work of independent engineer H L 'Bert' Fruin of Hillingdon, Middlesex, who constructed a series of technically interesting 'specials' in the 1950s and 1960s, including a DOHC 125cc twin-cylinder racer and a modular V4/V8 engine. Proprietor of H L Fruin Motorcycles in Hillingdon, Bert began competing on his Italian Demm-based 50cc two-stroke Dartela racers in the late 1950s and rode them at the Isle of Man TT in 1962 and 1963, retiring on both occasions. The first Fruin-built 200cc Four was featured in The Motor Cycle magazine (3rd May 1962 edition, copy on file), which also revealed his plans for future multi-cylinder 'strokers'.

Designed to accommodate Demm top-ends and later NSU Quickly components, Bert's four-cylinder engine was sold in kit form as a crankcase and set of crankshaft blueprints at a cost in 1961 of £16. The engine of the machine offered here was built by engineer Mike Smith of Waltham Abbey, Essex around 1965 and uses NSU cylinders and heads. It was fitted with Wal Philips fuel injectors initially and then Dell'Orto carburettors. Smith housed the Fruin engine in an MV Agusta rolling chassis fitted with Royal Enfield forks and Gilera hubs. Power reached the ground via a Villiers four-speed close-ratio gearbox. Motor Cycling magazine featured Smith's Fruin Four in its 24th July 1965 edition (copy available). The Fruin proved un-competitive in 250 class so Smith used it mainly for sprinting.

At some time in the 1980s Mike Smith sold the Fruin to Kevin Burton, who in turn passed it on to Tony Milk of New Costessey, Norfolk. In 1999 Mark Turner of Track & Classics, Stockport bought the bike from Tony Milk who had advertised it for sale in Old Bike Mart (copy on file). It is understood that the Fruin was run but never raced by Milk. Mark Turner made a new fuel tank and re-commissioned the Fruin, which was run at his shop in Stockport and again at a classic motorcycle event at Elvington Air Museum (see correspondence on file). While in Mark Turner's ownership the Fruin was the subject of an article in Classic Bike Guide (March 2000 edition, copy available).

Turner then sold the Fruin to a collector, from whom it was purchased by the current vendor and restored in 2009. Refurbishment included rebuilding the engine and gearbox, repainting the frame and fuel tank, re-plating the brightwork, overhauling the carburettors and float bowls, and rebuilding the wheels. The electrics remain original and un-restored. Following its restoration the Fruin was displayed on the Carole Nash stand at the NEC, Birmingham and also at the Stafford Show.