Guy Leslie Llewellyn Morgan was born in Hackney, London, England on 14 June 1902. He studied architecture at University College, London, and was awarded the Andrew Taylor Prize in Architecture in 1923. He was in practice as an architect from 1927. He was also a lecturer and Year Master at the Architectural Association in London from 1931 to 1936. By 1936 he was senior partner in the architectural practice Guy Morgan & Partners. The practice was active until at least 1965.
He was elected an Associate of the Royal Institute of British Architects (ARIBA) in 1926; and a Fellow of the Royal Institute of British Architects (FRIBA) in 1936.
His address was given as 11 King's Bench Walk, London in 1927; Sunneyside, Fetcham, near Leatherhead, Surrey in 1930; 9 Gower Street, London in 1935; 41 Lowndes Close, Belgrave Square, London in 1939; and 25 Belgrave Street, London in 1965. He died in Sussex on 25 July 1987.
Aircraft factories and air bases; office buildings; blocks of flats; town planning schemes and housing in England and other countries; agricultural buildings; country houses; sports stadia; and hospitals.