He was a Fellow and Curator Emeritus of the Drawings Collection of the Royal Institute of British Architects, founding Trustee of Save Britain's Heritage and Save Europe's Heritage, and founding member and Honorary Life President of the International Confederation of Architectural Museums.

[1] He travelled and took on miscellaneous jobs, before starting his proper career in 1954 working in an antiques shop, Collin and Winslow.

Harris founded and organised 42 exhibitions at the Heinz Gallery, on the ground floor of 21 Portman Square, opened in 1972, designed by Stefan Buzas and Alan Irvine, given by Mr and Mrs Henry J Heinz II,[4] being the first purpose built gallery for the display of architectural drawings in the English speaking world.

[5] The Gallery was purchased in 2000 by the Irish Architectural Archive and moved in 2003-4 to the ground floor of their relocated premises at 45 Merrion Square, Dublin, which opened to the public in 2005.

Harris was a co-curator of the seminal Destruction of the Country House exhibition held at the V&A in 1974, with Sir Roy Strong and Marcus Binney, which gave impetus to the movement to conserve British country houses[6] and the founding in 1975 of Save Britain's Heritage.