He was born in Glanton, Northumberland, England, the son of a doctor, and educated at Charterhouse and at Christ Church, Oxford in Classics and Modern History, later moving to Merton College, Oxford to be a research fellow. His home was a place largely devoid of affection, books and intellectual interests. Trevor-Roper took a first in Classical Moderations in 1934 and won the Craven, the Ireland and the Hertford scholarships in Classics. Initially Trevor-Roper intended to make his career in the Classics, but he became bored with what he regarded as the pedantic technical aspects of the Greats course at Oxford, and instead switched to History, where he obtained another first in 1936.. Trevor-Roper's first book was his 1940 biography of Archbishop William Laud, in which Trevor-Roper challenged many of the prevailing perceptions surrounding Laud.
For Trevor-Roper, the major themes of early modern Europe were those of intellectual vitality, religious quarrels and of divergence between Protestant and Catholic states, the latter being outpaced by the former economically, politically and constitutionally. European expansion overseas was incidental to these processes. In Trevor-Roper's view, one of the major themes of early modern Europe was that of expansion. By expansion, Trevor-Roper meant overseas expansion in the form of colonies and intellectual expansion in the form of the rise of nationalism, the Reformation, and the Enlightenment. In Trevor-Roper's view, the witch hunts of the 16th and 17th centuries were part of the reaction against growing doctrinal pluralism, and were ultimately traced back to the conflict between the rational worldview of such thinkers as Desiderius Erasmus and other humanists and the spiritual values of the Reformation.
Trevor-Roper argued that history should be understood as an art, not a science, and asserted that key attribute of the successful historian was the power of imagination. For Trevor-Roper, history was full of contingency, and the story of the past was neither a continuous advance nor decline, but was rather resolved by accident and through the particular choices that particular individuals made in the time at question. Though Trevor-Roper often acknowledged the impact of social trends upon history, in his view, it was the actions of the individuals that made the difference. However, in his studies of early modern Europe, Trevor-Roper did not focus exclusively upon politcal history, but rather sought to examine the interaction between the political, intellectual, social and religious trends of the period. Trevor-Roper's preferred medium for expressing himself was the essay rather the book. In his essays in social history in the 1950s-1960s, Trevor-Roper was increasingly influenced by, though he never formally embraced the work of the French Annales School, especially Fernand Braudel, and did much to introduce the work of the Annales school to the English-speaking world.
In Trevor-Roper's opinion, the dispute between the Puritans and the Arminians was a major, through not the sole cause of the English Civil War. For Trevor-Roper, the dispute was over issues of free will and predestination, of preaching and the importance of the sacraments, and only later over the structure of the Church of England. The Puritans desired a decentralized and more equal church with an emphasis on the laity while the Arminians wished for ordered church with a firm hierarchy with the bishops on top and an emphasis on the divine right and salvation via free will.
In 1960, Trevor-Roper waged a successful campaign against the candidacy of Sir Oliver Franks who was backed by the heads of houses marshalled by Maurice Bowra for the Chancellorship of the University of Oxford and had his old friend and publisher the Prime Minister Harold Macmillan elected instead. In 1964, Trevor-Roper edited a festschrift in honor of his friend, Sir Keith Feiling's 80th birthday. In 1970, Trevor-Roper was undoubtedly the author of The Letters Of Mercurius, a satirical work on the student revolts and university politics of the late 1960s.
As a historian of early modern Britain, Trevor-Roper was most famous for his disputes with fellow historians such as Lawrence Stone and Christopher Hill, whose materialist (and in some measure "inevitablist") explanations of the English Civil War he enthusiastically attacked. Trevor-Roper was a leading player in the so-called "storm over the gentry" (also known as the "gentry controversy"), a dispute with Christian Socialist R. H. Tawney and Stone about whether the English gentry were, economically, on the way down or up in the century before the English Civil War, and whether this had anything to do with the outbreak of that war in 1642. Stone, Tawney and Hill all argued that the gentry were rising economically, and that this caused the Civil War. Trevor-Roper argued that, whilst office-holders and lawyers were prospering, the lesser gentry were in decline and that was the Civil War's cause. A third group, revolving around J. H. Hexter and Geoffrey Elton, argued that the causes of the Civil War had nothing to do with either the alleged rise or decline of the gentry. In 1948, a paper put forward by Stone in support of Tawney's thesis was destroyed by Trevor-Roper who in a rancorous counter-essay showed that Stone had exaggerated the debt problems of the Tudor nobility. Trevor-Roper then attacked Tawney's theories concerning rising gentry and declining nobility, arguing that the latter was guilty of selective use of evidence and of misunderstanding the statistics.
Trevor-Roper's attacks on the philosophies of history advanced by figures like Arnold J. Toynbee and, the Marxist, Edward Hallett Carr and on his colleague A.J.P. Taylor's account of the origins of World War II, were also widely noticed. Another notable dispute was with Taylor and Alan Bullock over the question of whether Adolf Hitler had any fixed aims or not. In the 1950s, Trevor-Roper was ferocious in his criticism of Bullock for his portrayal of Hitler as a “mountebank” (i.e. opportunistic adventurer) instead of the ideologue that Trevor-Roper believed him to be. When Taylor offered a picture of Hitler similar to Bullock's in his 1961 book The Origins of the Second World War, the same debate continued, very publicly, between Taylor and Trevor-Roper. Another notable feud Trevor-Roper carried on in the 1950s-60s was with the novelist and Catholic convert Evelyn Waugh, who saw Trevor-Roper as a severe critic of his Church, and was often vocal in expressing his criticism of Trevor-Roper.
In regard to the Globalist-Continentalist debate between those who argued that Adolf Hitler had as his aim the conquest of the world, as against those who argued that he sought only the conquest of the continent of Europe, Trevor-Roper was one of the leading Continentalists. He argued that the Globalist case rested upon taking a wide scattering of Hitler's remarks over several decades and attempting to turn these views into a systematic ideology. In Trevor-Roper's opinion, the only consistent objective Hitler sought was the domination of Europe.
A notable thesis propagated by Trevor-Roper was the “general crisis of the 17th century”. Trevor-Roper argued that the middle years of the 17th century in Western Europe saw a widespread break-down in politics, economics and society caused by a complex series of demographic, social, religious, economic and political problems. In this “general crisis”, various events such as the English Civil War, the Fronde in France, the climax of the Thirty Years War in Germany, troubles in the Netherlands, and revolts against the Spanish Crown in Portugal, Naples and Catalonia were all manifestations of the same problems. The most important causes of the “general crisis”, in Trevor-Roper’s opinion, was the conflict between “Court” and “Country”; that is between the increasingly powerful centralizing, bureaucratic, sovereign princely states represented by the court, and the traditional, regional, land-based aristocracy and gentry representing the country. In addition, the intellectual and religious changes introduced by the Reformation and the Renaissance were important secondary causes of the "general crisis".
The “general crisis” thesis generated much controversy between those, such as the Marxist historian Eric Hobsbawm, who believed in the “general crisis” thesis but saw the problems of 17th-century Europe as being more social and economic in origin then Trevor-Roper would allow. A third fraction comprised those who simply denied there was any “general crisis” such as the Dutch historian Ivo Schöffer, the Danish historian Niels Steengsgaard, and the Soviet historian A.D. Lublinskaya. Trevor-Roper's "general crisis" thesis provoked much discussion which led to experts in 17th century history such as Roland Mousnier, J. H. Elliott, Lawrence Stone, E. H. Kossmann, Eric Hobsbawm and J. H. Hexter all weighting in on the pros and cons of the theory. At times, the discussion became quite heated with the Italian Marxist historian Rosario Villari, who speaking of the work of Trevor-Roper and Mousnier claimed that: "The hypothesis of imbalance between bureaucratic expansion and the needs of the state is too vague to be plausible, and rests on inflated rhetoric, typical of a certain type of political conservative, rather than on effective analysis". Villari went to accuse Trevor-Roper of speaking to downgrade the importance of what Villari called the English Revolution (the usual Marxist term for the English Civil War), and insisted that the "general crisis" was part of an idealistic Europe-wide revolutionary movement. Another Marxist critic of Trevor-Roper was the Soviet historian A.D. Lublinskaya who attacked the concept of a conflict between "Court" and "Country" as fiction, and thus argued there was no "general crisis"; instead Lublinskaya maintained that the so-called "general crisis" was merely the normal workings of the emergence of capitalism.
One of Trevor-Roper's most successful books was his 1976 biography of the Sinologist Sir Edmund Backhouse, 2nd Baronet, who had long been regarded as one of the world's leading experts on China. In his biography, Trevor-Roper proceeded to expose Backhouse's life-story and virtually all of his scholarship as a fraud. The discrediting of Backhouse as a source led to much of China's history being re-written in the West as many of Backhouse's assertions, such as his claim that the Dowager Empress ordered the murder of her son, were proven to be false.
The extent of Trevor-Roper’s influence can be seen in the list of contributors to History and the Imagination, the festschrift in his honor; some of the more notable contributors were Geoffrey Elton, Michael Howard, J.H. Elliott, Valerie Pearl, and Fernand Braudel.
Trevor-Roper's initial endorsement of the alleged Hitler diaries raised questions in the public mind not only about his perspicacity as a historian but also about his integrity, because The Sunday Times, a newspaper to which he regularly contributed book reviews and of which he was an independent director, had already paid a considerable sum for the right to serialise the diaries. Trevor-Roper denied any dishonest motivation, explaining that he had been given certain assurances as to how the diaries had come into the possession of their "discoverer" -- and that these assurances had been mistaken, prompting the satirical magazine Private Eye to nickname him Hugh Very-Ropey.
Despite the shadow that this incident cast over his later career, he continued writing (producing Catholics, Anglicans, and Puritans in 1987) and his work continued to be well received.
His brother, Patrick Trevor-Roper, was a leading eye surgeon and prominent gay rights campaigner, one of only three gays willing to testify before the Wolfenden Committee, which was investigating whether British law on this should be changed.
Hugh Trevor-Roper was awarded a life peerage in 1979 and chose the title Baron Dacre of Glanton, of Glanton in the County of Northumberland. He was the first life peer created by Margaret Thatcher in her term as Prime Minister.
Lord Dacre of Glanton died of cancer in a hospice in Oxford, aged 89. In his last years he had suffered from sight problems leading to visual illusions, problems which were corrected by surgery. Three books by Trevor-Roper were published posthumously. The first was Letters from Oxford, a collection of letters written by Trevor-Roper in the 1950s to his close friend, the wealthy American art collector Bernard Berenson, who lived in a villa outside of Florence, Italy. The second book was Europe’s Physician, an unfinished biography of Sir Theodore De Mayerne, the Franco-Swiss court physician at the courts of James I and Charles I. The latter work was a manuscript Trevor-Roper had largely written by 1979, but for reasons unknown did not finish the work. The third book was The Invention of Scotland: Myth and History, a critique written in the mid-1970s of what Trevor-Roper regarded as the myths of Scottish nationalism, and which was published in 2008.