 In 1938 he joined the J. Walter Thompson advertising agency, later moving to Lund Humphries printing in Bradford, Yorkshire.McLean was profoundly influenced by the work of Jan Tschichold, the German typographer, and he visited him at his home in Switzerland shortly before the outbreak of the Second World War.During the war, he served in the Royal Naval Volunteer Reserve, acting as the British Liaison Officer in the Free French mine-laying submarine, "Rubis", where he was in charge of the code books and, after each patrol, had to secretly report to the Admiralty on the morale of the French crew.