What is the longest running West End musical?

Les Miserables, running in London continuously since 1985 - close to forty years, which is longer than most of its audience has been alive. It was savaged by critics on opening; one review called it a lurid Victorian melodrama, and the producer Cameron Mackintosh reportedly considered closing it before word of mouth took over.

It is sung throughout with essentially no spoken dialogue, which is opera by any structural test, and it condenses a 1,400-page novel that includes long digressions on the Paris sewers and the battle of Waterloo. The barricade it centres on is not the 1789 revolution, which audiences routinely assume, but the June Rebellion of 1832 - a failed two-day uprising that most French people have never heard of.

The longest-running show in the West End overall is not a musical but The Mousetrap, playing since 1952 with a break only for the pandemic, and with an audience tradition of not revealing the ending. Agatha Christie signed away the rights as a birthday present to her grandson, and gave the play what she assumed was a run of a few months.