Educated at Elm Park Preparatory School, County Armagh, Sandroyd School, Winchester College and Christ Church, Oxford, he was called to the Bar in 1955.
Silsoe deliberately followed a career in planning law, his favoured area, rather than spending his life in law courts ("wig and gown" as he described it), an environment he did not particularly enjoy.
He was leading counsel for the proposers in notable public inquiries beginning with the Thorp nuclear fuel reprocessing plant and finishing with the Heathrow Airport Terminal 5 expansion inquiry.
Silsoe lived near Reading, Berkshire, and was an active member of the congregation at All Saints Church, Rotherfield Peppard, serving for some years on the Parochial Church Council.
He was instrumental in shaping the revised Henley deanery in the late 1990s.