He was born on 26 September 1948 in London. His family later moved to Somerset and Essex before settling in Berkshire. While at St Paul's School, London, he established a friendship with John Betjeman and, through him, links to literary London. In 1967 he went to Magdalen College, Oxford (B.A., M.A. - History). At the university he was a pupil of Karl Leyser, Hugh Trevor-Roper and Howard Colvin. He was also part of a group experimenting with psychedelic drugs. While an undergraduate he became a friend of the trans-sexual April Ashley (whose biography he later wrote ) and familiar with the 'Chelsea Set' of Swinging London.
In 1970, at the age of 21, Fallowell was given a pop column in the Spectator. He was subsequently the magazine's film critic and fiction critic. During the 1970s he travelled in Europe, India and the Far East, collaborated on the punk glossies Deluxe and Boulevard, and worked with the avant-garde German group Can. He began writing about Can's music in the British press in 1970 and visited the group in Cologne soon after. He explored other aspects of the German rock scene at the beginning of the 1970s, visiting Berlin, Munich and Hamburg. He wrote verbal covers to many of Can singer Damo Suzuki's non-linguistic vocals and when Damo left the band in 1973 Fallowell was asked if he'd like to take over as vocalist - 'after a long dark night of the soul,' he decided against it (see Prospect magazine March 28, 2008).
In 1979 he edited a collection of short stories, Drug Tales. This was followed by two novels, Satyrday and The Underbelly. Chris Petit reviewing The Underbelly for The Times wrote: 'The author's pose and prose is that of dandy as cosh-boy...The writing attains a sort of frenzied detachment found in the drawings of Steadman or Scarfe.'.
During the 1980s he spent much of his time in the south of France and Sicily, celebrated in the travel book To Noto. Patrick Taylor-Martin, reviewing it, wrote that the author was 'stylishly at ease with the louche, the camp, the intellectual, the vaguely criminal. His prose combines baroque extravagance with a shiny demotic smartness...He is particularly good on sexual atmosphere.'. His second travel book: One Hot Summer in St Petersburg, was the outcome of a period living in Russia's old imperial capital. Michael Ratcliffe, literary editor of The Observer, making it his Book of the Year, wrote that it 'combines, as exhilaratingly as Christopher Isherwood's Berlin writings, the pleasures of travel, reporting, autobiography...There is candour of every kind...an absolute knockout.'. Anthony Cross, Emeritus Professor of Slavonic Studies at the University of Cambridge, in his book on St Petersburg and the British, wrote that Fallowell's 'evocation of life in the new St Petersburg is a stunning tour de force... in the spirit of Nikolai Gogol'. Fallowell has said that 'My original title was Funky Dmitri but I was persuaded that the word funky would pass out of fashion - which it hasn't and it wouldn't have mattered if it had. I still think of the book by that title.'
It was while living in St Petersburg that he wrote the first draft of the libretto for the opera Gormenghast, inspired by Mervyn Peake’s trilogy. With music composed by Irmin Schmidt, this was first staged in 1998 at the Wuppertal Opera (Germany) which had commissioned it. Schmidt was a member of Can and Fallowell had already written the lyrics to two albums of his songs, Musk at Dusk (1987) and Impossible Holidays (1991) This work is also featured in Irmin Schmidt's compilation Villa Wunderbar (2013) and collection Electro Violet (2015).
A third novel, A History of Facelifting, draws on his experience of the Marches, the border country in Herefordshire and mid-Wales, which Fallowell discovered in 1972 when he first visited Hay-on-Wye at the invitation of Richard Booth. Fallowell has visited the area often since then, at times staying for long periods in remote cottages. A third travel book, Going As Far As I Can, recounted Fallowell's wanderings through New Zealand. Jonathan Meades described it as having the ghostly atmosphere of de Chirico's paintings: 'The text has the movement of a dream' (New Statesman Books of the Year 2008).
His books have been controversial - Bruno Bayley in Vice Magazine wrote that Fallowell has 'penned novels that people seem to have a tendency to burn'. In the same interview Fallowell told him that 'Fiction is such a turn-off word, not because I am against imaginative work - of course not - but because there is so much crap published as fiction. I am interested in literature. I am not interested in some commercial idea that is simply verbalised. I want high performance language operated by an expert.' Roger Lewis dubbed Fallowell 'the modern Petronius' in a recent book.
As a journalist Fallowell identified with the movement known as the New Journalism which advanced a literary form variously taking in reportage, interview, commentary, autobiography, travel, history and criticism. He has only ever worked free-lance. His work has appeared in The Times, The Sunday Times, Observer, Guardian, Independent, The Daily Telegraph, The American Scholar, the Paris Review, Tatler, Vanity Fair, Marie Claire, Playboy, Penthouse, Encounter, Tages Anzeiger, The Age, La Repubblica, New Statesman, Vice, and many other publications. He has often contributed to the intellectual monthly Prospect and has had columns in the Spectator, Evening Standard and several online magazines. A collection of Fallowell's interview-profiles, Twentieth Century Characters was described by Richard Davenport-Hines as 'like Aubrey's Brief Lives in twentieth-century accents. The effect is of a rich, energetic frivolity and passionate curiosity about human types.'
How To Disappear: A Memoir For Misfits was published in 2011 by Ditto Press, designed by Nazareno Crea; it was awarded the PEN/Ackerley Prize for memoir in 2012. Chairman of the judges, Peter Parker, commended it as 'A subtle, beautifully written and often very funny example of autobiography by stealth.' Alan Hollinghurst, in the Guardian Books of the Year, called it 'brilliant and haunting'. The Independent on Sunday said Fallowell 'writes like a spikier Sebald, alternating between acerbic witticisms and passages of voluptuous description.'
He has for many years conducted an unusual epistolary relationship with the Mexican artist Pedro Friedeberg, described in 'Why is a fish like a bicycle?', Spectator, April 11, 2015.
John Heygate Award 2014. Fellow of the Royal Society of Literature 2015.