PN Furbank: Prolific literary critic and biographer best known for his acclaimed account of the life of his friend EM Forster

Nick Furbank is most likely to be remembered for his two-part biography (published in 1978 and 1979) of the novelist EM Forster. In it his subject is affectionately filleted with forensic candour and first-hand knowledge, and it still dominates a market that has continued to generate a worthy biographical alternative.

It is unlikely that Furbank, a literary critic, had sought this position, for his portrait of Forster notably lacks any critical appraisal. While also praising it, Sir Frank Kermode aimed accurately for the niche it left with his sparkling critique Concerning EM Forster (2009), and gained new ground. Furbank privately declared the book to be "disagreeable", but also admitted that he hadn't in fact read it.

It wasn't the only substantive work on Forster that he didn't absorb: Wendy Moffat's 2010 award-winning A New Life was discarded after "only 40 pages, because I didn't agree with her following Christopher Isherwood's premise that to write about [Forster] you had to centre it on sex." This was misguided of him. Furbank liked Moffat personally and was troubled that he couldn't write to congratulate her.

Praise for his depiction of Forster had been lavish, as befits such a labour of love, but while his senses could be poignant he didn't always allow himself to go far enough: "One could imagine [knowing Forster] that he had a 'secret'… a notion that occurred to many of his acquaintances." Yet when Furbank was presented with the evidence of a secret, he demurred. Kermode notioned the raising of "a fence at which even the equable Furbank refuses"; shortfalls of which there were a number.

Forster befriended Furbank in 1947 as a result of meeting at the intellectual society, the Cambridge Apostles. There was a 41-year age gap between them. It was not an unfamiliar story, but they came from the same class, and for Forster (never mind what Furbank may have felt) this excluded anything exceeding friendship.

After five years of knowing one another, he began a diary in which encounters with Forster were recorded. They were not made in secret, and it was three years before Forster's death in 1970 that he asked Furbank to write about him for posterity, having pulled the plug on the first choice. Only JR Ackerley's biographer, Peter Parker, seems to have recorded that the preferred candidate to write about Forster would originally have been Ackerley, whose pre-eminence foundered on his poor memory.

Thus Furbank came third to the task, and applied the same scholarship given to his existing biographies of Samuel Butler (1948), Italo Svevo (1966) – a neglected Italian writer – and later to the French philosopher and academic, Denis Diderot (1992). They were more balanced between biography and criticism, combining penetrating vision on both counts in prose that characteristically flowed.

This was far from being the case whenever Furbank spoke: a lifelong stutter inhibited him mercilessly, disallowing the venting of whatever pressing matter got stuck in his throat, and rendering him incapable of saying right out what came to him. The contrast with his writing could hardly have been greater. At the heart of this constriction lay deep-rooted inhibition probably concerning his homosexuality, in which he had two debilitating role models: Forster and Alan Turing.

Turing's conviction for homosexuality in 1952 drew a ghastly punishment in the form of hormone injections; these amounted to chemical castration over the period of a year and also caused gynaecomastia, and led to his suicide in 1954. Furbank had met him in Cambridge after the war and they "saw lots of each other" until Turing moved to Wilmslow in 1948.

They remained very close and "often exchanged letters including about his troubles", despite Turing being continually spied on and his mail intercepted. Furbank found Turing "very attractive, in the sense of his mind was full of original ideas", though he declared his surprise at having been asked to become Turing's legal and literary executor: "But he was a surprising man, and I didn't like to turn it down." Always a safe pair of hands, he was the least likely person to blurt out anything that he might later regret.

Philip Nicholas Furbank was born into an unremarkable, middle class family in Surrey in 1920, and attended Reigate Grammar School. He read English at Emmanuel College, Cambridge, achieving a First in both parts of the Tripos, before serving from 1940-45 as a Corporal in the Royal and Mechanical Engineers.

In 1941 he suffered the loss of his elder brother who was killed in a flying accident. Thereafter he returned to academia, becoming a Fellow of Emmanuel from 1947-53. He spent six years from 1964 as an editor at Macmillans before returning to Cambridge as a King's Fellow from 1970-72.

By then he had been drawn to the more innovative concept of distance learning at the burgeoning Open University, which was in line with his socialist principles and could accommodate his paralysing stutter. He became a professor there from 1977-85, and was thereafter emeritus professor until 2003.

As a reviewer of books, he produced countless articles over many years including for London Review of Books and The New York Review of Books; working into his nineties, he was still contributing to The Threepenny Review in Berkeley. A compulsion to write kept him going. He completed the draft of a book on cinema and film theory in 2012, with neither publisher nor agent in mind – "Who's going to take on a 92-year-old?" he not unreasonably asked.

His reviews remained vigorous and on target. It was not unheard of, if he wished to review a book and another one had already been commissioned, to run two reviews together. This showed how little of himself he gave away, preferring to remain focussed on he meaning and accuracy of words. He even looked askance at the gay themes he chose to write about – "I used to have a homosexual friend…" began one review – rather as he looked askance from his chair at life passing by his little house in Kentish Town, encased by walls of books, Japanese prints and an enormous flat-screen TV.

A chair visible in the garden behind was where he would enjoy the sunshine, but his intellect never reconciled the attitudes to homosexuality which had changed over his lifetime, still getting stuck on being the product of an illicit union between a Latin and a Greek word.

JULIAN MACHIN

Philip Nicholas Furbank, writer: born 23 May 1920; died 27 June 2014.