Tony Blair describes his "green guru", Jonathon Porritt, as "one of the most prominent voices promoting green issues over the last 25 years".
Sir Jonathon was awarded a CBE in the Millennium Honours List
Born in London in 1950 and educated at Eton and Magdalen College, Oxford, he abandoned his training as a barrister at the age of 25 to become an English teacher at an Inner London Education Authority comprehensive.
He was a candidate for the Ecology Party in the 1977 local government elections, and in 1979 stood at the general election and for the European Parliament.
After serving as chairman of the party, now known as the Greens, from 1979 to 1980 and 1982 to 1984, he stood again as a candidate in the 1983 general election and 1984 European elections.
In 1984 he gave up teaching to become director of Friends of the Earth (FoE).
Under his leadership, its number of supporters rose from 12,700 to 226,300.
In 1996, he left FoE to set up a charity called Forum for the Future, which aims to persuade individual businesses to improve their environmental performance.
His work for the charity attracted the admiration of the prime minister, who appointed Sir Jonathon chairman of the new Sustainable Development Commission in 2000.
A hereditary Sir he was awarded a CBE in the Millennium Honours List of that year.
A married father of two daughters, he lives in Cheltenham, Gloucestershire.