Lord Parmoor: Banker who became an antiquarian bookseller when he took over the management of Bernard Quaritch

Milo Cripps, the fourth Lord Parmoor, had a precocious academic genius that lacked a comfortable outlet until he was drawn, by chance, into taking over the management of the long-established antiquarian booksellers and publishers Bernard Quaritch in 1972. Under his hand the company grew, adapting itself to a changing market, and it remains one of the leading firms in the trade.

Nothing in heredity would have predicted this. The Crippses were a long-established, wealthy country family. Milo's grandfather, Charles Cripps, the first Lord Parmoor, was a successful lawyer and churchman who drifted into politics through a desire to see the boundaries of church and state properly defined. This achieved, he became a passionate advocate of the League of Nations, and through this a strong supporter of both of Ramsay MacDonald's governments. He married Theresa Potter, sister of Beatrice Webb and Kate Courtney, with whom he had five children, of whom Milo's father, Fred, was the second. Stafford Cripps, Chancellor of the Exchequer under Clement Attlee, was the youngest.

Colonel Fred Cripps was a brilliant horseman who joined the Buckinghamshire Yeomanry in 1907 and commanded it from 1917, leading the last-ever cavalry charge against the Turkish guns at El Mughar. In peacetime, he was a keen sportsman. He married late, in 1927, to Violet, daughter of Sir William Nelson and previously married to the second Duke of Westminster. She was his equal on a horse; the Duke had chartered special trains to take her equipage to meets. Naturally imperious, she also ran Douglas's, the fashionable hairdressers in Conduit Street.

Neither of them knew what to do with their late-born, gifted, wayward son. From birth, Milo Cripps subscribed to Edward Browne's view of the horse: "Noble animal, dangerous at both ends". His mother was a Catholic, so he went to Ampleforth whence, age 16, he won a classical scholarship to Corpus Christi College, Oxford. He was too young to go up immediately, so went to Paris to learn French. While there he stayed with a Russian family, so learnt Russian as well. Languages came to him naturally, and during national service in Berlin he worked as an interpreter.

Already by now the bottle threatened to take over, not in the alcoholic's secret over-indulgence, but in great public binges that often ended with him flat out. When he reached Oxford, he read not classics but philosophy, politics and economics, but his career was more memorable for the wild parties he gave – was it for his birthday, or his car's, that he celebrated by filling the car radiator with champagne in Berkeley Square? He left Oxford with no idea of what to do next.

He started the Flavian Trading Company, named after the Roman emperor for whom he felt an affinity, wholesaling odd and attractive things to smart shops. He invented "Matelotion – stimulates the follicles", to be sold at Douglas's. But by 1960 it all seemed to be going nowhere, until with a great effort and apomorphine he managed to stop drinking.

At about the same time, his mother happened to meet her neighbour Siegmund Warburg in Eaton Square; in something like despair, she asked him if he could find a job, no matter how lowly, for her son. Thus Cripps found himself in the filing department of the investment bank S.G. Warburg.

Miss Falk, the department's redoubtable head, was astonished to find Cripps not only willing but able in this humdrum but essential business. When he moved on, leaving Miss Falk disconsolate, he showed the same ability in other departments. This soon got back to Warburg himself, who always had a sharp eye for bright young men, and in no time Cripps was on a quick upward spiral; he became a director in the investment branch by 1964. There seemed no limits to opportunity, and in 1970 Cripps and his by now close friend George Warburg, Siegmund's son, set up their own firm, CW Capital.

One of its new clients was Jocelyn Baines, head of Thomas Nelson, the publishers. Seeing decline ahead, Baines wanted to move into the antiquarian book trade. Just then, the lease on Quaritch's old shop in Grafton Street fell in, and it moved to the cavernous premises of an old textile firm off Golden Square. Simultaneously, the Quaritch family was prepared to relinquish ownership, and CW Capital formed Antiquarian Securities Ltd (ASL) as a vehicle to take over the firm in 1971. Baines became managing director of Quaritch, and got Jon Bannenberg as decorator: green baize lined the walls and shelves, and massive pillars were painted brown and red. Meanwhile, ASL began to look around for other, similar businesses to add to its portfolio.

But the following year Baines died, suddenly and prematurely, and Cripps was obliged to step in as acting manager of Quaritch on behalf of ASL. CW Capital grew and became Cripps Warburg, but injudicious property lending got it into difficulties, from which it was rescued by its principal shareholder, Williams & Glyn's Bank, in 1975. Cripps, now without the backing of his own firm, decided to buy Quaritch. He took a majority share-holding, his great friend Simon Sainsbury the rest.

From now on Quaritch was the mainspring of Cripps's life. He had no interest in old books per se, but he enjoyed the company of a very diverse staff, which did. He read a lot in many languages (his army German had been useful at Warburg's, while Spanish came from his mother's family connections with Argentina), and could keep up with his employees in most of the literature of Europe. He also kept a watchful eye on the bottom line, was quick to check unprofitable investment, but as quick to stimulate competition between departments and to seize opportunities.

In 1977 Cripps succeeded as the fourth Lord Parmoor. In the same year, Quaritch negotiated the sale of the US book-collector Carl Pforzheimer's copy of the Gutenberg Bible, sold to the University of Texas, following it in 1986 with Pforzheimer's collection of early English literature. Learning that the great German banker Hermann Abs had put together a consortium to buy the Gospels of Henry the Lion, sent for sale by its family owners in 1983, Parmoor masterminded a successful bid that secured it for Germany. After buying the manuscript of Turgenev's Fathers and Sons in 1988, he wrote direct to Raisa Gorbachev as chairman of the Soviet Cultural Foundation to ask if the foundation would buy it. It did, and next year he took pleasure in seeing the manuscript in its new home in the Pushkin House in St Petersburg.

Individual triumphs like these were overshadowed by one colossal coup. In 1980 Quaritch bought the New York Horticultural Society's library for the Belgian collector Robert de Belder. When he later got into difficulties, Quaritch bought his entire botanical collection and set about looking for a buyer. They failed: the colour-plate books were too expensive, the ordinary books too many. So they sent the former to Sotheby's in May 1987; the sale was an extraordinary success, vastly exceeding all prediction. As a result, Parmoor was able to buy out the Sainsbury shareholding, and buy too the freehold of the building of which Quaritch owned part.

He had always enjoyed travelling, and did so more now. A visit to Australia left him in raptures. He went to Spain and thought of living there. But the beauty of the Manor House at Sutton Veny in Wiltshire, with shutters painted by William Nicholson, who had once lived there, always drew him back.

Milo Cripps was a generous and frequent godfather, generous, too, to friends in adversity, and as generous if discriminating to larger charities; he was a long and constant supporter of the Howard League for Penal Reform. He was an authority on newts, and did much to preserve the rarer species. The parties he gave were as good as ever, for all that he no longer drank. His wit crackled continuously: "Taste is a thing other people don't have"; "Fashion is a hard master".

In 2004, desirous of leaving Quaritch in good hands, he sold it to John Koh, seeing in him some of the qualities that had drawn him to it almost 30 years earlier. In June, knowing he was soon to die, he gave two last parties, one for book-trade friends, one for others. Better, he thought, their company while alive than a memorial service he couldn't himself be the life and soul of.

Nicolas Barker

Frederick Alfred Milo Cripps, banker and antiquarian bookseller: born London 18 June 1929; succeeded 1977 as fourth Baron Parmoor; died Bradford-on-Avon, Wiltshire 12 August 2008.