In the spring of 1983, the London Review of Books published a review of The Official Sloane Ranger Handbook: The First Guide to What Really Matters in Life. It was deeply serious and learned, beautifully written and structured, and made a convincing case that the authors of the handbook were better at undertaking anthropological fieldwork than they were at engaging with sociological theory. It was also a hilarious piece of academic self-parody, which concluded by regretting that neither the authors nor their publishers had recognised that “they had a bigger bestseller on their hands than even Malinowski’s Sexual Life of Savages in NW Melanesia”. It was scarcely coincidence that the review was published on the first of April. And it was equally unsurprising that the author of this sparkling piece was WG Runciman, the distinguished sociologist, who has died aged 86.

Runciman’s magnum opus was A Treatise on Social Theory (1983-97), a trilogy that sought to marry theoretical analysis and empirical observation, to demonstrate the appropriateness of this methodology by offering in the final volume a sociological history of 20th-century Britain, and to reinvigorate a subject that seemed to have lost its way. Yet Runciman had little time for disciplinary boundaries, and he ranged widely across the humanities and social sciences, publishing articles on topics as varied as the origins of states in ancient Greece, accelerating social mobility in Anglo-Saxon England, and charismatic legitimacy and one-party rule in Ghana.

Walter Garrison Runciman, invariably known as Garry, was born in London, the only child of Katherine Schuyler Garrison, whose forebears had been significant figures in gilded age New York, and (Walter) Leslie Runciman, who inherited his family’s shipping business and chaired the trustees of the National Maritime Museum. The Runcimans were a north-country dynasty, whose rise to fortune and fame was a classic story of upward social mobility.

Garry’s great-grandfather, Walter Runciman, was a self-made, Tyneside-based shipping magnate, who later became MP for Hartlepool, and was given a peerage in 1933. His grandfather, another Walter, held office throughout the Liberal administrations of 1905-16, later served in the national governments of the 1930s, was a committed appeaser at the time of Munich, and was created Viscount Runciman of Doxford in 1937. Garry’s father succeeded to the title in 1949; his younger brother, Steven, invariably described by Garry as “my wicked uncle”, became a distinguished medievalist, and fellow of the British Academy. This was a formidable pedigree, in which entrepreneurship, public service, high academic achievement and abundant social connections were all to be found.

During the second world war Garry was shipped off, like many upper-class children, to the US, and on his return followed what was by then the conventional family path of Eton and Trinity College, Cambridge (where he took firsts in both classics and history), interrupted by national service in the Grenadier Guards. Already, as a Trinity undergraduate, he was spoken of as the cleverest man in Cambridge. He then went to Harvard as a Harkness fellow, returning to Trinity as a research fellow in 1959.

His first book was Plato’s Later Epistemology (1962), but by then, influenced and encouraged by Robert K Merton of Columbia University, he had resolved to become a sociologist, a subject scarcely practised in British universities at that time, beyond the confines of the London School of Economics. The immediate result was Relative Deprivation and Social Justice (1966), a path-breaking study which stressed the importance of the gap between material measures of inequality and individual perceptions of their own social and economic circumstances.

In 1963, Runciman had left Trinity to take up the career in business that his father had hoped and expected he would embrace, and 13 years later he became chairman of Walter Runciman plc, the family’s shipping company, which meant, as he later noted, that he was “a practising capitalist” as well as an academic sociologist. He expanded the business, and saw off one hostile takeover, but in 1990, having by now succeeded his father as 3rd Viscount, accepted an offer of £65m from the Swedish company Avena.

He was president of the General Council of British Shipping in the late 1980s, and from 1991 to 2005 he was chairman of Andrew Weir, another shipping company. Both as a capitalist and a sociologist, Runciman was fascinated by the processes whereby societies accumulated and distributed wealth, and in 1986 he joined the Securities and Investment Board, soon after its creation as the overseeing authority of the big bang era; he was its deputy chairman from 1990 until 1998, by which time it had evolved into the Financial Services Authority.

Such was Runciman’s double life, but there was also a third string to his bow, as a public-spirited member of the liberal establishment. At different times, he was treasurer of the Child Poverty Action Group and a member of the board of the British Library. In 1991, the then home secretary, Kenneth Baker, asked Runciman to chair a royal commission into the criminal justice system. This followed several serious miscarriages of justice, including the Guildford Four and the Birmingham Six, whose bombing convictions from the 1970s had recently been quashed as unsafe by the court of appeal.

Runciman’s report was published in July 1993, and contained 352 recommendations, covering every aspect of the criminal justice system. Its most concrete and influential proposal was the creation of the Criminal Cases Review Commission to investigate future potential miscarriages of justice. In general, royal commissions are the means whereby controversial issues are tranquillised and marginalised: but in the case of Runciman’s landmark inquiry, the very opposite was true.

Even as he lived this triple-harness life, academia remained Runciman’s deepest passion and abiding interest. During the late 1960s, he was a part-time reader in sociology at the University of Sussex, and in 1971 he returned to Trinity as a senior research fellow, thereafter spending one day a week in Cambridge.

Four years later, he was elected a fellow of the British Academy, and between 2001 and 2005 served as its president, overseeing its centenary celebrations and editing an academy report examining the events, controversies and legal issues surrounding the invasion of Iraq in 2003. Unsurprisingly, he did not warm to New Labour.

Among his last works were Great Books, Bad Arguments (2010), in which he argued that Plato, Hobbes and Marx had all just got things wrong, and Very Different, But Much the Same (2014), which analysed the historical development of modern Britain, drawing on applied neo-Darwinian social theory. To the end of his life, Runciman never lacked intellectual self-confidence.

Very tall, very rich, very grand and very clever, he could sometimes seem aloof or intimidating. Yet despite his ancestry and attainments, he was surprisingly shy and diffident, and when he relaxed among friends, he was exceptionally congenial company. Behind the slightly forbidding exterior, he could be mischievous and funny, and he was never wholly at ease as a card-carrying member of “the great and the good”. In more ways than one, he was a towering figure, to whom that over-used word polymath does scant justice.

He is survived by his wife, Ruth (nee Hellmann), a leading activist in the fields of mental health, drug abuse and prison reform, whom he married in 1963, and their son, David, and two daughters, Lisa and Catherine.

• Walter Garrison Runciman, Viscount Runciman of Doxford, born 10 November 1934; died 10 December 2020