Hamilton followed his mother as a Christian Scientist, and attended Claremont Fan Court School and then Eton College.
He remained in the City for only a short period, leaving when he inherited two estates from his father's cousin.
He succeeded his father as Baron Hamilton of Dalzell in 1990, inheriting land near and properties in the village of Betchworth in Surrey, and a Regency mansion.
He was a strong Eurosceptic, opposing his party on issues relating to the Common Agricultural Policy and on the Maastricht Treaty.
Unusually, perhaps, he supported a written constitution, which he saw as a means to inhibit the gradual loss of power to Europe.
The database recording the 650 national plant collections run by the organisation was created under his chairmanship.