[1] On leaving school, Mackay trained as a quantity surveyor and later volunteered for the Royal Air Force in 1941, but was not accepted because of a perforated eardrum.

In 1962, Mackay appeared at the same theatre, in Russian playwright Maxim Gorki's play The Lower Depths for the Royal Shakespeare Company.

He is best remembered for his namesake role from 1973 to 1977 as the comically ferocious prison officer, Mr Mackay, in the British sitcom Porridge, alongside Ronnie Barker.

The ensemble playing of Mackay, Barker, Richard Beckinsale and Brian Wilde, and the writing by Dick Clement and Ian La Frenais, made Porridge one of the most successful comedy series of the 1970s.

[4] He returned to the role of Mr Mackay, now nearing retirement from HM Prison Service, in the first episode of Going Straight (1978), the sequel series to Porridge.

[5] Mackay often stayed true to his Scottish roots, acting in productions such as Play for Today's Three Tales of Orkney, in 1971, and The Master of Ballantrae, and as former Prime Minister Bonar Law in the 1981 TV series The Life and Times of David Lloyd George.

After his screen debut in the film I'm a Stranger (1952), his most notable roles were those in Gumshoe (1971), Britannia Hospital (1982), Local Hero (1983), and Defence of the Realm (1985).

[7] His Dalhousie's Luck, a drama set at the time of the siege of Aberdeen by the Marquess of Montrose in 1644, produced by Pharic Maclaren and with Brian Cox in the title role, was broadcast as part of the Play for Today series on 3rd August 1980.