In the following decades, Trevor-Roper expressed and developed his interest in Gibbon in many ways. He lectured on Gibbon to history undergraduates at Oxford, having sponsored the introduction of the "Gibbon and Macaulay" paper to History Mods. He gave papers on Gibbon in England and abroad. He published reviews and journalism which brought Gibbon, and new publications about Gibbon, to the attention of the general public. He crafted a series of scholarly articles that explored the substance and significance of the Decline and Fall, and the character of its author. And he lent his weight and authority to the re-publication of Gibbon's own writings — the reprint of A Vindication in 1961; the abridgements of the Decline and Fall for which he wrote introductions in 1963 and 1970; and, as an appropriate coping-stone, his substantial introduction to the six-volume complete Decline and Fall published by Everyman in 1993.

So Trevor-Roper's interest in Gibbon was long-lived and found many forms. But it was also sharply defined. He was unconcerned to explore the bibliography of Gibbon's writings, and he disdained to sink too deeply — indeed, at all — into the mud of textual criticism. Some of the more memorable sallies in his reviews of publications on Gibbon were dictated by his disdain for those he saw as the myrmidons of Gibbonian scholarship, and their depraved appetite for the dust of textual minutiae; as when he crushingly judged Joseph Ward Swain's Edward Gibbon the Historian to be a book which "positively subtracts from knowledge". But if he had explored Swain's book more patiently, he would have found in it quotations from manuscripts at Yale which Lord Sheffield had composed, but finally discarded, when publishing Gibbon's Miscellaneous Works in 1796 — manuscripts which, as it happened, had the power to enrich and strengthen Trevor-Roper's own interpretation of the nature and importance of Gibbon's achievement, at least in the material question of his attitude towards religion in general, and towards the outcry against chapters 15 and 16 in particular.

Furthermore, although Trevor-Roper relished Gibbon's prose, he did so like a historian. In all his writings on Gibbon, he proceeds on the assumption that style is a kind of varnish applied as a final seal for the historical canvas. The contrary view, that style might be more intimately and fundamentally related to the substance of historical thought, was not a possibility to which Trevor-Roper's mind warmed. Indeed, he more than once characterised Gibbon's most tremendous strokes of style as ignes fatui that threatened to distract his readers from the substantive significance of the Decline and Fall, and thereby allow a marvellous triumph of historical thought and imagination to be valued too lightly as a work of mere persiflage.

If bibliography was the occupation of pedants and style was more to be enjoyed than analysed, what, for Trevor-Roper, was the significance of the Decline and Fall for the man of educated, liberal mind? Going through his papers (now preserved in the archives at Christ Church, Oxford), and seeing how Trevor-Roper set about preparing a lecture or an article on Gibbon, one is confronted by a concrete image of a fact about his writings on this subject. The often bewildering mass of fragments of earlier typescripts, to which small strips of new manuscript might be pinned or clipped, or bridging text precariously appended, and the unsentimental slicing up and incorporation of earlier offprints into later work, makes visually plain the fact that throughout his publications on Gibbon there was a core of a few details of the historian's biography, and a few — indeed, surprisingly few — passages of the Decline and Fall, to which Trevor-Roper returned time and again. What constituted this core?

First, Trevor-Roper would lay heavy emphasis on the importance of Gibbon's removal from Oxford after converting to Catholicism, and his consequent translation to Lausanne, which his father had imposed on him so that he might become again a compliant Protestant. From this episode, Trevor-Roper drew two consequences. The first, and less important, was that the débacle of Gibbon's time at Oxford and his withdrawal from the University had put the pre-eminent historian outside the "historical guild". Trevor-Roper often reflected with deep satisfaction on the fact that Gibbon had been no professional historian, but had pursued his researches and composed his unrivalled narrative unsupported by any institution and in the character of a private scholar. Gibbon's estrangement from the "historical guild" made him, too, a foe of those "solemn professionals" against whom Trevor-Roper himself, throughout his career, waged implacable war. Gibbon was thus an important early member of that informal and engaging party with which Trevor-Roper always associated himself — the party of "the laity and the gaiety".