Born at Hessle, Yorkshire, as Michael Delanoy Walker, his mother was Kathleen Harvard (née Johnson), and his father, Eric Delanoy Walker, was a company director. Michael was moved from Yorkshire to London when he was two years old. He went to Bedford School but was unhappy there and ran away at the age of 13.
He entered National Service in 1952 as a lieutenant in the Royal Armoured Corps, and served, mainly in Egypt, until 1954. It was during this time that Walker became aware of and embraced his homosexuality, joking years later that he fainted during a parade exercise in honor of Queen Elizabeth's 1953 coronation not from the heat but because "the colour sergeant was so beautiful."
At the age of 20 in 1954 he joined the Bedfordshire Times as a reporter, and he stayed there for three years until, in 1958, he moved to the Brighton and Hove Herald as a reporter and feature writer. He left the paper after it was discovered that he was creating his reports of the football matches at the Brighton & Hove Albion ground using the coverage of the matches printed in the Brighton Argus. From 1961 to 1962 he was editor of the in-house journal of Richard Thomas & Baldwin, a national steel-making company.
In 1962 he joined Prism Publications and he became assistant editor of Prism, the radical church voice of the time. In 1963 the Reverend Tim Beaumont, later Lord Beaumont of Whitley, gave him a job as part of a team at Lambeth Palace producing a group of magazines including Time & Tide. Michael De-la-Noy was given responsibility for Outlook, a new-style insert for parish magazines.
In 1966 he joined Robert Maxwell's Pergamon Press where he edited educational books. At the age of 33 he stood for election to the General Assembly of the Church of England, and was returned as a lay representative for the diocese of London. At one time he ran a country-house hotel.
In 1967 he was appointed as press officer to Michael Ramsey, the Archbishop of Canterbury, and accompanied him to Bermuda, the West Indies, America, and Sweden. However, three years later he was dismissed after writing two articles on sexual deviation in magazines. One was about a transvestite Army colonel in Forum, and the other was in New Society and described in frank terms the life of a bisexual man.
Michael De-la-Noy ascribed his dismissal to a Machiavellian plot by the establishment to oust him, fuelled by the press. As a result he had a nervous breakdown and eventually lost his faith. He described his sacking in A Day in the Life of God, (1971), in which he was able to refer to a letter from Michael Ramsey who wrote that he had made a great blunder and asked for forgiveness.
In 1970 he was appointed as director of the Albany Trust and in 1971, Secretary of the Homosexual Law Reform Society (HLRS) and he stayed in the job for about eighteen months. It was also in 1971 that De-la-Noy first met his life partner, Bruce Hodson.
From 1975 to 1977 he worked at the Open University as an editor of its publications. He caused controversy when he wrote an article in the student publication Sesame, in which he discussed the suspension of the chair of the Paedophile Information Service. In a later article he explained that he was not advocating paedophilia. However, this article attacked lazy, incoherent dons.
In the 1980s he began to write biographies, particularly of gay men including Denton Welch and the Bishop of Southwark, Mervyn Stockwood, who was gay but celibate. Michael De-la-Noy also edited an unexpurgated edition of Denton Welch's journals in 1984. However, his book on Edward Sackville-West in 1988 got him into trouble when he described Edward Sackville-West's love affair with Jack McDougal, who was Evelyn Waugh's publisher. Some of Jack McDougal's letters were quoted in breach of copyright and the book had to be withdrawn and reprinted.
He occasionally wrote obituaries for The Independent and The Guardian. These included Mervyn Stockwood, James Lees-Milne, Kay Dick, Cuthbert Bardsley, David Herbert, and Kathleen Farrell. He also contributed to the New Dictionary of National Biography.
In the 1990s he wrote from his home in Hove a number of letters to the press defending homosexuals and complaining of breaches of etiquette. In a letter written just two months prior to his death, De-la-Noy responded to an editorial claiming that recognizing gay marriages would destroy the church by writing,
"Sir, My same-sex relationship was blessed by an Anglican priest 31 years ago. We are still together, and I have no recollection of the Anglican Communion falling apart." (A letter to The Times, June 2002)
He died of cancer aged 68, in Kettering, Northamptonshire, leaving Bruce Hodson, his partner of 31 years. Michael De-la-Noy had written his own obituary for The Independent some years before his death, and had put some final touches to it the day he suffered a major stroke at the end of July 2002. This was the first time that The Independent had published an auto-obituary.