Happy birthday for 'Les Mis'

The theatre impresario will host a gala performance of the show, directed by Sir Trevor Nunn, and a party afterwards. Joining the cast on stage for the finale will be 35 amateur child actors to mark Les Miserables' unparalleled success in schools.

Three years ago "Les Mis" became the first musical still playing in the West End to be available for school to stage with the publication of a special edition.

Since then there have been almost 3,000 school and under-19 amateur productions in Britain and America.

Sir Cameron said: "More than 100,000 children have taken part in the productions - we get stacks and stacks of letters at the office. This shows that Les Mis is as alive today as it was 20 years ago."

The professional production is only a year short of breaking the record of Cats as the longest-running musical in the history of the West End.

Yet when it opened at the Barbican, even Sir Cameron dared only to dream it would run for about four years. The show, which has starred Michael Ball, Ricky Martin, Roger Allam and Ruthie Henshall, has now played 40,000 times in 38 countries and 242 cities.

It has been seen by almost 55 million people and taken more than £1billion at the box office. So much for the critics.