[1] Kay was born in Coventry, Warwickshire, the son of Frances (née Petty) and Charles Beckingham Piff.
He went to the Royal Academy of Dramatic Art (RADA) and in 1957, after graduation, joined the Radio Drama Company by winning the Carleton Hobbs Bursary.
He created the roles of Jimmy in Arnold Wesker's Roots (1959) and Charles V in John Osborne's Luther (1961).
He remained until 1966, during which time he portrayed a wide variety of roles, including Octavius Caesar in Julius Caesar, Clarence in The Wars of The Roses, Launcelot Gobbo in The Merchant of Venice, Antipholus of Ephesus in The Comedy of Errors, Osric in the David Warner Hamlet, Dobchinsky in The Government Inspector and Moloch in Robert Bolt's The Thwarting of Baron Bolligrew.
His numerous appearances on television include Crown Court, Jennie: Lady Randolph Churchill in which he played Montagu Phippen Porch, Fall of Eagles in which he played Tsar Nicholas II, I, Claudius, The Devil's Crown, To Serve Them All My Days, By the Sword Divided, Fortunes of War, Rumpole of the Bailey, The Citadel, Edge of Darkness, The Darling Buds of May, Jonathan Creek, Law and Disorder, Hetty Wainthropp Investigates, Holby City, Midsomer Murders and The Casebook of Sherlock Holmes story "The Creeping Man".