he largest supplier of proprietary motorcycle engines in the world, J. A. Prestwich & Co (aka JAP), decided to go racing with something unique in 1922.In a matter of weeks, a small team headed by Val Page, aided by Herbert Le Vack, had produced a radical new design - the first British double-overhead-camshaft motorcycle racing engine. With this amazingly advanced engine fitted to a New Imperial frame, Le Vack stunned his competitors at the 1922 Isle of Man TT. From then on the engine and its successors proved invincible - breaking numerous National and World Records over a four-year period. Yet the subsequent world recession, and a world war, consigned these achievements to memory and eventually bestowed upon them an almost mythological status. JAP-s engineering archives were discarded, and the handful of engines made might well have been lost too had it not been for a series of enthusiasts.In Le Vack-s Legacy, Brian Thorby traces the fortunes of the small number of JAP racing engi
