Winston was born in Witney, Oxfordshire when the family were on holiday. He grew up in Chatsworth House and has inherited that property. He went to a private school in Oxford, before attending Oxford University, with Arthur Gordon-Lennox.
He succeeded his father as Duke of Devonshire in May 2002 when he died suddenly following a fatal car crash. He was then entitled to a Conservative House of Lords Peerage which he accepted. He was always a keen public speaker and political campaigner.
He was elected as the Member of Parliament for Witney after he resigned his Conservative House of Lords peerage to sit in the House of Commons. He was a backbench MP until 2017 when he became Secretary of State for Defence in the George Wellesley administration.
Soon after, George Wellesley resigned and Cavendish put his name forward in the Conservative Leadership Election. He was unopposed as remaining candidates stood down from the election.
The following day, he was invited to form a government by The Queen. He accepted, and kept most of the cabinet the same, apart from appointing George Wellesley interim Chancellor of the Exchequer and First Secretary of State. Following this, George Wellesley resigned after about a week as Diana Ponsonby took office as Chancellor of the Exchequer and Deputy Prime Minister. Following Ponsonby's resignation a few weeks later, Arthur Gordon-Lennox became Chancellor, but the Cavendish administration was criticised for the constant cabinet reshuffles with led to a motion of no confidence in the Government in the House of Commons. Cavendish and his government resigned the next day and a General Election was called, which was ran by the Liberal Democrats.
On the 10th of March, whilst visiting Syria's President on a governmental visit, it is believed that Winston Cavendish's body was found dead by a governmental motorcade. The body found had several wounds and a major head trauma. It has not yet been confirmed if it was Winston Cavendish.
Winston was found alive in a Finnish Hospital, and Finnish Officials confirmed he was alive. This led to his return to the UK. He has since took up a place in the House of Lords and has made a rivalry with Arthur Gordon-Lennox, his former Foreign Secretary.
Due to David Cavendish succeeding him as Duke of Devonshire, he was given the title of Marquess of Reading, an extinct title his mother's side of the family held.