John Anthony Crook, ancient historian: born London 5 November 1921; Assistant Lecturer in Classics, Reading University 1948-49, Lecturer 1949-51; Fellow, St John's College, Cambridge 1951-2007, Tutor 1956-64, President 1971-75; Assistant Lecturer in Classics, Cambridge University 1953-55, Lecturer 1955-71, Reader in Roman History and Law 1971-79, Brereton Reader 1974-79, Professor of Ancient History 1979-84 (Emeritus); FBA 1970-80; died Cambridge 7 September 2007.

Though he would certainly have dismissed the idea, because he was invincibly counter-suggestible, as well as enjoying an international scholarly reputation and occupying the chair of Ancient History at Cambridge, 1979-84, John Crook occupied a unique place in the affection of colleagues, pupils and staff at St John's College, where for 55 years he occupied the same set of rooms, kept his oak permanently unsported, and, in the offices he successively held, came to symbolise the place for generations of old members whom he would welcome back as to their home. Every year, the weeks before Christmas were given over to the writing of letters to scores of former pupils.

A Balham boy and the only child of parents of limited means, Crook's early career provided a wonderful vindication of the old LCC scholarship system, which took him to Dulwich College, where his linguistic and musical gifts were nurtured, and in 1939 to St John's.

Having taken a First in Part I of the Classical Tripos, in February 1942, he was drafted into the 9th Royal Fusiliers, with whom he served in the Middle East and North Africa before being captured on landing in Italy and sent to Stalag Luft VIIIB in Silesia, where he acquired fluent German, taught languages to other prisoners, perfected his remarkable skill on the clarinet (the instrument his father, a military bandsman, played), and developed as a Shakespearean actor, a side of him later deployed at the lecturing dais and, memorably, when as President of St John's he descended Malvolio-like to disperse a group of roistering junior fellows at their cups.

After completion of the Tripos with another First, a year in Oxford and a spell at Reading, in 1951 he returned to Cambridge as a research Fellow of St John's. His Consilium Principis (1955) established him as a front-rank historian of antiquity, but with ancient history treated as an ancillary subject within Classics and as one which, he strongly believed, should be taught straight from the source material, one of the reasons why he was such a great admirer of A.H.M. Jones, his predecessor-but-one as professor. He was an expert on rhetoric and was a superb lecturer, using movement and facial contortion, as well as voice, gown and an impeccable sense of timing, to capture and hold an audience. He would invariably have a full house at 9am.

Apart from the respectful bowing of the head, it was the Crookian nose that was the principal prop: marvellously mobile, it maintained a Pat-and-Mike act with its sympathetic chin as he pretended to have forgotten the end of one of his endless fund of stories. Narrowing his eyes, his expression – calculating but also self-deprecatory – might as easily resolve itself into a jeremiad bewailing the latest manifestation of Crook's Law ("Everything is getting worse") as into the generous laugh, which was never exactly a laugh but was sometimes a murmur, sometimes almost a cackle, delivered with head thrust forward, gnathic gestures, and arms set back like rudders.

He was particularly in his element at college meetings ("Master, I have a difficulty"; "Master, the council has got this wrong") but was not one to rock the college boat unless he was certain it was rowing dead steady, which Crook's Law stated it rarely was. At gatherings of the College Classical Society, which for 50 years met in his rooms, he would reminisce and chat about anything under the sun. His particular passion was to get the society singing in Latin, the favourite being "Waltzing Matilda", with its chorus starting "ambiclitella! ambiclitella!" (Latin for swag).

Roman law was his main interest. His work was a model for Roman historians who shared this interest, and he stimulated others to work in the field. His Law and Life of Rome (1967) was his most important and influential work. At the same time he had an ambiguous relationship with "professional" Roman lawyers, as a tribe, as opposed to individuals who got to know him and appreciated his scholarship. This was partly his own doing. Law and Life has, instead of the usual dedication, a "warning" to the experts to stay away: "iuris consultus abesto". Perhaps this was tongue-in-cheek; perhaps he was laying down a challenge. For he was not always easy to fathom.

In his Legal Advocacy in the Roman World (1995) he vigorously championed the status and the calling of advocates (and rhetoric) as opposed to jurists (and jurisprudence), taking up a position not unlike that of Cicero, the great advocate himself, but with the additional goal of rehabilitating rhetoric in the eyes of modern scholars. To an unusual degree, the authentic voice, colloquial yet elegant, was audible in the printed word.

Crook was a demanding but sympathetic teacher of undergraduates. He took enormous trouble and time over graduate students and junior colleagues. He was especially good at working through difficult texts with them, and read their work readily and carefully. Although the arena of his own research was traditional, revolving around Roman political and constitutional history, and Roman law, he typically took a critical line, and encouraged the young to do the same. If they seemed to be edging towards a novel, even risky, interpretation, he would egg them on and urge them to state their case strongly.

He was a princely host – and a princely guest – a man of infinite courtesy, carefully indicating the architectural features of the college courts to passing strangers who had only stopped him to ask if there was a loo. His generosity was legendary, and secret. He could be generous because he was careful. "Two Coxes from the stall with the man with the funny leg," he would specify when I went to do his shopping. The blotting paper on his desk said a lot about him. It had a 1951-ish look about it, and its blottingness appeared marginal, but because some little areas of white remained, there it stayed. Only relatively recently did he capitulate to use of a fountain pen.

Sometimes grumpy ("I'm grumpy today"), he adhered to old-fashioned standards, being one of the small number of fellows of the British Academy to resign in protest at the failure of that body to expel Anthony Blunt. "Expert in law, expert in justice both", in the words of the translation of Guy Lee's dedication in Thinking Like a Lawyer, the "Crookschrift", as he called it, which he was delighted to receive on his 80th birthday. The most filial of sons, he had eschewed matrimony on account of his eccentricities, he said, but bitterly regretted bachelorhood. He was never happier than when crawling on the floor with small children; and as they grew up and showed an aptitude for languages in presenting them with dictionaries. Sharing with that other old Alleynian P. G. Wodehouse a strong liking for school stories, he rejoiced at the eventual triumph of Harry Potter. For him, the greatest change in the college in his lifetime had been the lowering of the age of majority, not the admission of women (which he had strongly championed).

While still capable of doing his own shopping, with plastic mac flying he was, as one of the local shopkeepers observed, "part of the furniture of Trinity Street". During an earlier stay in Addenbrooke's, where he died, the ex-POW had reasserted himself as self-appointed ward-orderly. While reading the Iliad in the original with a gentleman of the road (happily called Hector) whom he discovered to have had the beginnings of a classical education, he was kept busy restraining an elderly clergyman from pulling his medical moorings off the wall. "He doesn't know whether he's got his trousers on or not," he confided, "but he's still perfectly sound on the doctrine of the Trinity."