Originated in France as an album and then briefly as a show. Cameron Mackintosh got hold of it and the English show opened at the Barbican Centre in 1985. Moved first to the Palace and then on 3 April 2004 to Queen’s. The “world's longest running musical” claim is disputed by Wikipedia who awards that prize to ‘The Fantasticks’ (42 years) with Les Mis coming in second. But they confirm it is the longest-running musical in the West End.