In addition to his establishment background, interest has been fuelled by his decision to turn his back on a promising political career. Now 51, he was tipped to become a cabinet minister by 30.
He served in the Wilson and Callaghan governments, becoming a Northern Ireland minister of state before becoming disillusioned with party politics. The end of his political career is said to have occurred in the mid-1980s after he answered a call by anti-nuclear protesters for recruits whose arrest would attract publicity.
He went to a US airbase in Norfolk and was trying to cut the wire when the former Conservative MP Lady Olga Maitland - then a pro-nuclear campaigner - shouted: "Peter, Peter, don't do it; it'll ruin your career." A year later he had become head of Greenpeace.
A Greenpeace spokeswoman said Lord Melchett had cut his ties with the Lords and returned only to vote for abolishing the hereditary principle.
He has fronted headline-grabbing campaigns for Greenpeace, including the Brent Spar protests against Shell, which won the movement admiration for its campaigning abilities, though it was accused of fabricating evidence.
More recently he added to the problems facing the organisers of the Millennium Dome when he said the PVC waterproof coating was poisonous. The dome organisers hit back, saying it posed no risk to the public.
Lord Melchett has a home in Islington, London, where he lives with his partner and two children. He also has a 750-acre organic farm in Norfolk.Reuse content