Hampstead theatre, LondonThe quicksilver actor is a vocal glory as the poet and classicist AE Housman looking back at his younger, tormented self in Tom Stoppard's play A man arrives at the underworld. "I'm dead, then," says AE Housman. "Good." Tom Stoppard's 1997 play conjures the poet and classicist, whose heart and mind were brimming but who never quite lived " decades-long adoration for a man who couldn't love hi…