THERE IS A saying that good plays are not written but rewritten and it can equally be argued that the test of a play’s strength is not the premiere but ­revivals. The work of Sir David Hare has passed this examination well, with several of his texts – including Plenty, Racing Demon and Amy’s View – proving more critically ­admired and/or commercially prosperous in much later restagings.Now Skylight, a National Theatre, West End and Broadway success from 1995-97, returns, just ahead of its twentieth anniversary, as one of the year’s most coveted tickets in a revival at Wyndham’s Theatre until 23 August with two movie stars – Bill Nighy and Carey Mulligan – under the direction of Stephen Daldry, who graduated from stage work (such as h