Alwyn Gwilym Sheppard Fidler was born in Holywell, Flintshire, Wales on 8 May 1909. In 1927 he enrolled at Liverpool University, School of Architecture where he was taught by Charles Herbert Reilly and Patrick Abercrombie. In Summer 1931 he gained work experience in the office of Zantzinger, Borie & Medary in Philadelphia. He graduated in 1932 and was awarded the RIBA Victor Scholarship and the Rome Scholarship in 1933. He was elected an Associate of the Royal Institute of British Architects (ARIBA) in 1933. He worked as an assistant in the offices of Grey Wornum and Herbert James Rowse in 1937.
Fidler was appointed Chief Architect to the Land Settlement Association in 1937; and Chief Architect to Barclays Bank in 1938. During World War Two he served as a senior technical intelligence officer in the Ministry of Homeland Security. He left the Ministry in 1946 and the following year was appointed Chief Architect to Crawley New Town. He was first City Architect of Birmingham from 1952 to 1964. During his tenure he oversaw major new road schemes in the city and a massive programme of slum clearance and tower blocks.
In 1964 Fidler left Birmingham and moved to London where he set up his own architectural and town planning practice, A. G. Sheppard Fidler & Associates. He later relocated the practice to Epsom, Surrey.
Fidler received Civic Trust Awards for his work on Lydhurst Estate and Hawkesley Moat Farm Estate in Birmingham in 1961. He was chairman of the Architects’ Registration Council of the United Kingdom (ARCUK, 1960–63) and of the British School at Rome (1972–87).
In 1974 Fidler retired to Reigate, Surrey where he died on 4 January 1990
Works by Fidler's practice included architectural projects in collaboration with the civil engineering firm W. S. Atkins & Partners. Among these were a structure plan for Shannon New Town, Ireland (1972); the Podium shopping centre in central Bath (1989), and, with several other partners, other partners, the Arabian Gulf University, Bahrain. One of Fidler's most successful commissions was Bournehall library and social centre in Epsom (1965–70).
Sharples, Joseph, Powers, Alan and Shippobottom, Michael. Charles Reilly & the Liverpool School of Architecture 1904-1933. Catalogue of an exhibition at the Walker Art Gallery, Liverpool, 25 October 1996 - 2 February 1997. Liverpool: Liverpool University Press, 1996 p. 170 [Contains other references to Fidler, unfortunately, the catalogue is not indexed]