Joan Littlewood’s greatest disservice to the theatre was to champion ‘the right to fail’, which encouraged writers and directors to inflict a thousand shades of bilge on play-goers for many decades. But she deserves a place in the pantheon for an inspired decision taken in 1959. Offered a new play about Soho’s underworld, written by the ex-con Frank Norman, she invited a young pop composer to turn it into a larky musical.