His younger brother Nicholas Ridley, Baron Ridley of Liddesdale was a Conservative Party politician who served as a government minister for nearly all of Margaret Thatcher's years as prime minister.

The Second World War interrupted his education and he joined the Coldstream Guards, serving in Normandy and Germany in 1944–45.

He then studied at Oxford, graduating with a degree in Agriculture from Balliol College in 1948.

In 1955, Ridley and zoologist Lord Richard Percy spent four months on an uninhabited island in the Seychelles studying the plight of the dwindling sooty tern.

He retired in 1999 and did not stand for election as a hereditary peer after the House of Lords Act.