MORE than 14 years ago Bill Kenwright surprised many (and possibly himself) by reviving Willy Russell’s Blood Brothers, which had run for a few months in the West End in 1983. Now the musical play is a set text, it has enjoyed a two-year stint on Broadway, and, to judge by a recent matinee, is still getting standing ovations in London. So the question arises: what’s the pull of its tale of the twins who are separated at birth and, as we’re warned at the start, come to a joint end in terror and violence?