Humphreys was the son of Travers Humphreys, himself a noted barrister and judge. His given name "Christmas" is unusual, but, along with "Travers", had a long history in the Humphreys family The Blavatsky Trust: Christmas Humphreys. Among friends and family he was generally known as 'Toby' The Blavatsky Trust: Christmas Humphreys. He attended Malvern College, where he first became a theosophist and later a convert to Buddhism, and Trinity Hall, Cambridge; he was called to the bar by the Inner Temple in 1924.

The same year, Humphreys founded the London Buddhist Lodge, which later changed its name to the Buddhist Society. The impetus for founding the Lodge came from theosophists with whom Humphreys socialised. Both at his home and at the lodge, he played host for eminent spiritual authors such as Nicholas Roerich and Dr Sarvapalli Radhakrishnan, and for prominent Theosophists like Alice Bailey and far Eastern Buddhist authorities like D.T. Suzuki. Other regular visitors in the 1930s were the Russian singer Vladimir Rosing and the young Alan Watts. The Buddhist Society of London is one of the oldest Buddhist organisations outside Asia.

When he had first qualified, Humphreys tended to take criminal defence work which allowed his skills in cross-examination to be used. In 1934, he was appointed as Junior Treasury Counsel at the Central Criminal Court (more commonly known as "the Old Bailey"). This job, known unofficially as the 'Treasury devil', involved leading many prosecutions.

Humphreys became Recorder of Deal in 1942, a part-time judicial post. In the aftermath of World War II, Humphreys was involved in the War Crimes trials held in Tokyo. In 1950 he became Senior Prosecuting Counsel. It was at this time that he led for the Crown in some of the causes célèbres of the era, including the Craig and Bentley case and Ruth Ellis and it was Humphreys who secured the conviction of Timothy Evans for a murder later found to have been carried out by Reg Christie. All three cases played a part in the later abolition of capital punishment in the United Kingdom.

Also in 1950 at the trial of the nuclear spy Klaus Fuchs, Christmas Humphreys was the prosecuting counsel for the Attorney General.: The World's Greatest Spies and Spymasters by Roger Boar and Nigel Blundell, 1984 In 1955 he was made a Bencher of his Inn and the next year became Recorder of Guildford.

Allegations

Writer Monica Weller has alleged that Humphreys manipulated evidence in the trial of Ruth Ellis, changing witness statements, in order to secure her conviction. Melford Stevenson « Searching for the Truth about Ruth Ellis By Monica Weller

In 1982 at the Buddhist Society in London, Ruth Ellis's son Andre McCallum secretly taped a conversation with Humphreys (Source: Ruth Ellis: My Sister's Secret Life, Andre McCallum) where he said the following:

"As a barrister for 50 years I was just putting the facts of the actual murder. I knew nothing of the background and I didn't care."

"So you still think there was an injustice in that she [Ruth Ellis] was found guilty of deliberate murder when she wasn't?"

"It [mercy] never came into my mind because, you must understand, how we play in parts as if on a stage. I have my part to play. Defending counsel has his. The judge has his. The jury have theirs... Mercy never came into it. It was never suggested. It was never part of it. There could be no mercy in what seemed to be cold-blooded murder."

"I think I said to the jury, 'Members of the jury this is to all intents and purposes a plea of guilty.'

Ruth Ellis had actually pleaded not guilty at her trial in June 1955.

In 1962 Humphreys became a Commissioner at the Old Bailey. He became an Additional Judge there in 1968 and served on the bench until his retirement in 1976. Increasingly he became willing to court controversy by his judicial pronouncements; in 1975 he passed a suspended jail sentence on a man convicted of two counts of rape. The Lord Chancellor defended Humphreys in the face of a House of Commons motion to dismiss him, and he also received support from the National Association of Probation Officers.

Humphreys was a prolific author of books on the Buddhist tradition. He was also president of the Shakespearean Authorship Society, which advanced the theory that the plays generally attributed to Shakespeare were in fact the work of Edward de Vere, 17th Earl of Oxford. He published his autobiography Both Sides of the Circle in 1978. He also wrote poetry, especially verses inspired by his Buddhist beliefs, one of which posed the question: When I die, who dies?

• An Invitation to the Buddhist Way of Life for Western Readers
• Both Sides of the Circle London:George Allen & Unwin. Humphreys's autobiography (1978).
• Buddhism: An Introduction and Guide
• Buddhism: The History, Development and Present Day Teaching of the Various Schools
• Buddhist Poems: a Selection, 1920-1970
• A Buddhist Students' Manual
• The Buddhist Way of Action
• The Buddhist Way of Life
• Concentration and Meditation: A Manual of Mind Development
• The Development of Buddhism in England: Being a History of the Buddhist Movement in London and the Provinces (1937)
• Exploring Buddhism
• The Field of Theosophy
• The Great Pearl Robbery of 1913: A Record of Fact (1929)
• An Invitation to the Buddhist Way of Life for Western Readers (1971)
• Karma and Rebirth (1948)
• The Menace in our Midst: With Some Criticisms and Comments, Relevant and Irrelevant
• One Hundred treasures of the Buddhist Society, London (1964)
• Poems I Remember
• Poems of Peace and War (1941)
• A Popular Dictionary of Buddhism
• A Religion for Modern Youth (1930)
• The Search Within
• Seven Murderers
• Sixty Years of Buddhism in England (1907-1967): A History and a Survey
• Studies in the Middle Way: Being Thoughts on Buddhism Applied
• The Sutra of Wei Lang (or Hui Neng) (1953)
• Via Tokyo
• Walk On
• The Way of Action: The Buddha's Way to Enlightenment
• The Way of Action: A Working Philosophy for Western Life
• A Western Approach to Zen: An Enquiry
• The Wisdom of Buddhism
• Zen A Way of Life
• Zen Buddhism
• Zen Comes West: The Present and Future of Zen Buddhism in Britain
• Zen Comes West: Zen Buddhism in Western Society

In addition, Humphreys edited several works by Daisetz Taitaro Suzuki

• Awakening of Zen
• Essays in Zen Buddhism (The Complete Works of D. T. Suzuki)
• An Introduction to Zen Buddhism
• Living by Zen
• Studies in Zen
• The Zen Doctrine of No Mind: The Significance of the Sutra of Hui-Neng (Wei-Lang)

and co-edited

• Secret Doctrine by H.P. Blavatsky
• Mahatma Letters to A.P. Sinnett

and wrote forwards/prefaces to

• Buddhism in Britain by Ian P.
• Diamond Sutra and the Sutra of Hui-neng (Shambhala Classics) by W.Y. Evans-Wentz (Foreword), Christmas Humphreys (Foreword), Wong Mou-Lam (Translator), A F Price (Translator)
• Essays In Zen Buddhism (Third Series) by D.T.Suzuki
• Living Zen by Robert Linssen
• Mahayana Buddhism: A Brief Outline by Beatrice Lane Suzuki
• Some Sayings of the Buddha

Van Morrison refers to Humphreys in his 1982 song "Cleaning Windows," which appears on the album Beautiful Vision.