An understudy at the Royal Shakespeare Company has written a remarkably indiscreet diary of going on a world tour with Sir Ian McKellen’s King Lear. It describes back-stage bitching, bed-hopping and a cast mutiny against director Sir Trevor Nunn. There is even a night in New York when Sir Ian misses a cue because he had fallen asleep. An embarrassing pause is blamed on a technical fault, but it was really because the star’s dresser had forgotten to make sure he stayed awake backstage. The salty diary has been written by veteran actor David Weston, who followed Sir Ian all year. It is in many ways a serious, fascinating book about the unsung role of understudies. But it could cause a severe attack of the vapours in luvvie-land when it is published in September. It certainly ignores the old saw, what goes on tour stays on tour. In Covering McKellen, Mr Weston describes selfishness among the company’s younger actors, not least arrogant film star Romola Garai. Sir Trevor emerges as an unpredictable, distant, even neglectful figure who loses the loyalty of his actors. The cast becomes sloppy and disengaged, and an uprising occurs in Minnesota after Sir Ian is rough with an actress on stage. The production became notorious because Sir Ian’s Lear dropped his trousers in one scene, revealing an instrument of Shakespearean proportions. Mr Weston suggests that Sir Ian, a great gay rights campaigner, adored all the attention paid to his undercarriage. Eccentric Frances Barber (Goneril) is depicted enjoying a bad review given to a rival actress. Mr Weston, who calls the cast ‘the most dysfunctional company I ve ever been part of’ , also has a go at us theatre critics. The beast! In the event, Mr Weston never did get to step in for Sir Ian, who is such an old trouper that he was never off sick. But the understudy did play Lear in a special rehearsal. The moment came to drop his trousers. Whoosh! At which point a party of schoolgirls entered on a tour of the theatre . Screams all round