Hugh Trevor-Roper, who has died aged 89, became a life peer as Lord Dacre of Glanton in 1979 and was arguably the leading British historian of his generation. He was surely the most versatile and eloquent. He was also a vivid personality, fearless of orthodoxies and fashions, whose distinctive political and intellectual philosophy drew him, in the course of a crowded life, into a succession of memorable public controversies, not least the "Hitler Diaries" fiasco.
Born the son of a country doctor in Northumberland, he acquired, during a solitary childhood, the love of literature and the feeling for language that would inform everything he wrote and said. He was educated at Charterhouse and Christ Church, Oxford.
Christ Church, with its social confidence and worldly connections, drew him out. He transferred as an undergraduate from classics to history. From 1937 to 1939 he was a research fellow of Merton College, Oxford, where he wrote his first book, Archbishop Laud (1940).
During the war he served in the Radio Security Service and the Secret Intelligence Service, working on the penetration and deception of the German secret service. Later he drew on that experience in The Philby Affair (1968).
More immediately, the war and its aftermath produced the classic that made his name, The Last Days Of Hitler (1947): a claustrophobic, Tacitean portrait of dissolving tyranny which is also a work of investigative genius.
At the end of the war he had been commissioned by the intelligence services to discover what had happened to Hitler, whom Stalin was claiming was still alive. Trevor-Roper travelled through Germany, tracking down and interrogating survivors of Hitler's court and reconstructing not only the circumstances of the Führer's death but the power structure of his regime.
In 1946 he returned to Christ Church, now as a student. He quickly became a leading force in the college, where he was censor from 1947 to 1952. Meanwhile his historical research had reverted to 17th-century England. An instinctive and sometimes merciless controversialist, he was soon engaged in the "storm over the gentry", in which he took on R.H. Tawney and Lawrence Stone over the economic causes of the English civil war. This was one of the most fertile historical debates of modern times, its interpretative influence long outlasting the original points of dispute.
But Trevor-Roper's interests could not be confined to a single period or country. His reviews and essays in the press, ranging widely in subject matter, reached an audience well beyond the academic community. In 1957 he published a combative collection of short pieces for the general reader, Historical Essays. In the same year, at 43, he was appointed to the Regius professorship of modern history at Oxford, a position he held, in conjunction with a fellowship at Oriel, until 1980.
Throughout his career he resisted, against the current of the time, the tendency of the academic community and of the historical profession towards introversion. Yet his objection was only to narrowness of vision, never to scholarship. The aspect of his tenure that he most enjoyed was his part in the scholarly training of Oxford's expanding postgraduate population. He was the most devoted and inspiring of teachers.
His tenure was colourful. He was quickly involved in a celebrated dispute with A.J.P. Taylor, who had been a rival for the chair, over Taylor's The Origins Of The Second World War.
In 1959 he challenged academic introversion on another front, taking on the powerful and, to his mind, stuffy heads of Oxford colleges, successfully to champion prime minister Harold Macmillan's chancellorship bid.
He has left behind an extraordinary range of scholarly writing, not all of it completed or published. But the world, he felt, was not short of fat books on single subjects. His favoured form was the essay, sometimes the long essay - where insight must be concentrated, proportion maintained and the evidence of learning kept mostly beneath the surface.
Comparison was his essential intellectual instrument, as it was of the "philosophic historians" of the 18th century, Gibbon at their head, whom he admired. Everything that interested him seemed to remind him of something else.
In 1967 he brought together perhaps the most remarkable of his collections of essays, Religion, The Reformation And Social Change. Employing an almost dizzying range of material, the book centred on the revolutions that shook Europe in the middle of the 17th century, and related them to the mental ferment that preceded and accompanied them.
It also marked the movement of his thinking away from economics to ideas. They were the boldest exposition of lifelong persuasions: of his equation of historical progress with pluralism; of his impatience with closed intellectual systems (both past and present); and of his rejection of historical determinism.
He had a strong satirical impulse and sense of mischief. He was reputedly the author of The Letters Of Mercurius (1970), comical vignettes of the Oxford of the time of student revolt, which ran in The Spectator.
In 1980, aged 66, he moved to Cambridge as Master of Peterhouse, where his conflict with what he saw as an enclosed and reactionary oligarchy among the fellows became another cause célèbre.
In 1985, he was asked to authenticate 60 volumes that became known as "the Hitler Diaries" for the London Sunday Times. The paper was serialising the diaries, which had been "discovered" in Germany.
Trevor-Roper, after examining the material for what he later said was "a few hours only", announced that the books had been written by Hitler and were genuine. Unfortunately for his reputation, the volumes were forgeries. Both the forger and a reporter for Germany's Stern magazine, who was in on the hoax, went to prison for the forgeries. Trevor-Roper, who came under a hail of professional and press ridicule, issued a public apology for his mistake.
When he retired from Peterhouse in 1987 he had embarked on a series of collections of essays which had appeared in scattered places, and which in a number of cases he now substantially rewrote.
He remained an essentially private, even shy, man. In his 80s, his mind as alert as ever, he bore a gradual loss of sight and the advance of cancer with stoical fortitude and good humour, sustaining a scholarly correspondence around the globe. His wife Alexandra died in 1997. They had been devotedly married for 43 years. He is survived by three stepchildren.
Hugh Redwald Trevor-Roper, Baron Dacre of Glanton: born January 15th, 1914; died January 26th, 2003