Smith and his wife, Christian Carnegy, founded the Landmark Trust in 1965, to rescue and restore decaying and redundant buildings of architectural or historic interest and give them a new future by letting them for holidays.
He also dabbled in politics, and was Conservative MP for the Cities of London and Westminster from 1965-70.
At the same time Smith became deeply involved with environmental concerns, which grew parallel with his financial and political careers.
Smith became a member of the Historic Buildings Committee with the National Trust, and it was through his work with the trust that he noticed many smaller, but worthwhile historic buildings were falling through the conservation net.
To combat this, he created the Landmark Trust, and stood at the helm for 25 years, during which time 125 buildings were restored and made available for holidays.
Smith resigned as chairman of the trustees in 1990 but thanks to his organisation, buildings such as Pugin's The Grange (AJ 13.07.06), could be saved.
Martin Drury, chairman of the Landmark Trust, said: 'Everyone at Landmark feels a deep sense of loss at the passing of Sir John.
'He was an inspiration to us all and we are enormously proud to work for the organisation he created. His sublimely simple formula for breathing new life into historic buildings is a precious legacy to the nation and will enrich the lives of all who care for our built heritage for years to come.'
Sir John Smith: born 3 April 1923, died 28 February 2007