Born in 1951, in Dunfermline, Fife, Allan became interested in snorkelling and diving after watching Jacques Cousteau’s film, The Silent World, a 1956 documentary which was one of the first to use underwater filming.
After graduating with a degree in marine biology from the University of Stirling, he took on a number of diving jobs.
His big break came when he was taken on as a research diver with the British Antarctic Survey, stationed at Signy Island in the South Orkney Islands.
He was later awarded the Polar Medal, an honour he would win twice, for his work.
In 1981, a chance meeting with Attenborough led to Allan working on the documentary series Living Planet, part of which was filmed in the Antarctic.
He began specialising in filming in some of the planet’s most extreme environments.