Born in Southampton, the only child of Ernest Mais, a Master Mariner, he was educated at Banister Court School, Hampshire, before attending the College of Estate Management, where he trained as a surveyor.
During World War II Mais served as a major with Special Forces in France, Iran and Iraq.
After returning to Britain late in 1943, his orders were to develop the Mulberry harbour project for the D-Day landings.
He then joined the Canadians in the advance to the Rhine and, promoted full colonel, became deputy chief engineer at Antwerp.
After the War, Mais joined contractors Trollope & Colls, becoming joint-managing director and chairman in 1963 and retiring in 1968 when the firm was taken over by Trafalgar House.