After studying at RADA, Glaister made his West End debut in 1939. With the outbreak of war, he joined the Royal Air Force, initially flying a Blenheim bomber and later serving as a photo reconnaissance pilot in 208 Squadron RAF in the Western Desert initially flying Westland Lysanders. It was during these latter duties that he was awarded the Distinguished Flying Cross for a hazardous reconnaissance flight in an unarmed Hurricane at extremely low level across the Italian front line. Glaister later drew on his RAF experiences when, in 1963, he produced Moonstrike, a drama about an RAF squadron which ferried agents in and out of occupied Europe in Westland Lysanders.
His 1968 production The Expert is based on the work of his uncle, forensic scientist Prof John GlaisterFRSE.