text: He returned to films with The Night Digger (1971), a horror film with Patricia Neal and was in episodes of Take Three Girls, Armchair Theatre, and Love Story.
  Clay had the starring role of Charles Darwin in The Darwin Adventure (1972) and was in William: The Life, Works and Times of William Shakespeare (1972). He was cast in several of Laurence Olivier's Old Vic productions and during the 1970s came to be regarded as one of British theatre's most promising actors. At the National Theatre he played Aumerle in Richard II, Giovanni in Tis Pity She's a Whore (directed by Roland Joffe), Nugget in Equus, a Jumper in Jumpers (directed by Peter Wood), Rocca in Saturday Sunday Monday (directed by Franco Zeffirelli), Young Seward in Macbeth (directed by Michael Blakemore) and Acaste in The Misanthrope. Blakemore also directed him in the part of Young Inna in Arturo Ui at Nottingham Playhouse, where Clay acted several roles in Jonathan Miller's production of King Lear. He played Hastings in Clifford Williams's world tour of She Stoops to Conquer. The Misanthrope led Clay to the United States, where he also played this role on Broadway in 1975. On the West End stage, Clay was Maurice in Flint (Criterion Theatre) and Trigorin in The Seagull (Cambridge Theatre).