McDonald was born in Bishopbriggs in 1937, the son of Jessie (known as Jeanette) Helen Low and Alexander M.
[2] He worked in the timber industry in the 1950s, prior to National Service in the Royal Air Force.
His role as Moderator of the General Assembly of the Church of Scotland meant he was one of the public figures who led tributes to Diana, Princess of Wales upon her death in 1997 in a BBC broadcast.
In May 2008, he made a non-speaking cameo appearance in the Doctor Who episode "The Unicorn and the Wasp", playing the part of a footman alongside his son David Tennant.
[5] McDonald was married to Helen (daughter of former footballer Archie McLeod) for over 40 years until her death on 15 July 2007.