After a series of false starts, Milo Cripps gained considerable success as an investment banker and went on to clinch a number of famous deals as an antiquarian bookseller.

Frederick Alfred Milo Cripps was born in 1929. His father, Colonel Frederick Cripps, the second son of the first Baron Parmoor, had been wounded at Gallipoli. The Labour politician and Chancellor of the Exchequer Sir Stafford Cripps was his uncle. His mother, Violet Nelson, was the daughter of Sir William Nelson, of the Nelson shipping line; she married Colonel Frederick in 1927 after her divorce from the second Duke of Westminster. She was a fine horsewoman; horses and hunting were her life. As a sensitive 17-year-old, Milo accompanied her and the Aga Khan to a nightclub. There they packed him off to dance with the Aga Khan’s wife, Rita Hayworth. While they talked about horses, Milo harangued Hayworth about existentialism; her answer was an oft-repeated “Huh?”

Cripps’s parents’ marriage, which ended in divorce in 1951, produced a contradictory, many-sided man of inflexible integrity, exuberant in everything. One friend summed Cripps up by saying that he was fired at a whiter heat than the rest of us. Whatever his mood, saintly or diabolical, sweet tempered or foul, he was more so.

From Ampleforth — like his mother, Cripps was a Roman Catholic — he won a scholarship to Corpus Christi College, Oxford. His military service took him to Berlin, which he loved; for 50 years he spent Christmas there, in the company of his lifelong friend Hermann Kopplin. He was a fine linguist, fluent in, among others, Russian, Catalan and Schweizerdeutsch.

In 1954 he founded and ran the Flavian Trading Company to sell new design, but it never took off. In 1955 he tried accountancy but found it tedious. In 1957 he was briefly researcher to Randolph Churchill, who was writing a life of Lord Derby. Cripps admired Randolph’s judgment in politics but resigned because he could not stand the screaming.

Despite his enormous talents, Cripps was achieving little, and it seemed drink would undo him. He said the last straw came when he gate-crashed his mother’s dinner party, rugby-tackled the principal guest and was sick all over the floor. However, with great willpower he fought the drink, and although he took his last drink in 1964, he would always refer to himself as an alcoholic.

In 1960 his mother begged her neighbour in Eaton Square, Sir Siegmund Warburg, to find her son a job at his firm, the investment bank SG Warburg. By the time Cripps started in the menial filing department his days of staggering round to his tailor after lunch to order 12 suits in which to watch polo were over. He threw his energies into the job, hurtling up through other departments, and in 1964 was made a director of the bank. Warburg said he had never met a more brilliant intellect.

In 1969 Cripps left SG Warburg, and with Siegmund’s son George, by now a firm friend, formed CW Capital — later named Cripps-Warburg — a fringe bank which in 1971 conducted the purchase of the antiquarian bookshop Bernard Quaritch from the Quaritch family on behalf of Antiquarian Securities (ASL). Jocelyn Baines, then head of the publishers Thomas Nelson, was appointed managing director of Quaritch, but late in 1972 he died, and Cripps became managing director. Cripps-Warburg came to grief in 1975 through unfortunate involvement in property investment, the fate of many such banks at the time.

Cripps founded the Sizewell European Trust with George Warburg in the late 1960s to allow people in Britain to invest elsewhere on the Continent. Although something of a visionary venture at the time it flourished under a board of European bankers, chaired by Cripps.

In 1975 Cripps bought Quaritch, taking a majority shareholding, with his close friend Simon Sainsbury. Ten years later the success of Quaritch allowed him to buy his partner out. Asked when he had become interested in books, he said: “I’m not. I blotted my copybook in the City and I’m too snobbish to sell ice-cream. I wanted a desk for life, somewhere to go in the afternoons.” To the end of his life he regarded himself as a banker, an entrepreneur.

Cripps threw himself into the book trade with ferocious energy. The negotiation of the sale of the Pforzheimer copy of the Gutenberg Bible to the University of Texas, the sale of the manuscript of Turgenev’s Fathers and Sons to the Soviet Cultural Foundation — negotiated by Cripps through Raisa Gorbachev — and above all the sale of the de Belder collection are legends in the book trade.

He was of immense help to any member of staff struggling to write a complicated catalogue, although his quick temper, once aroused, was fierce. He was unpredictable, yet wherever he was there was laughter. He both envied and admired his married friends.

He loved Wiltshire and some of his most contented moments were spent casting a fly on the River Wylye. In 1987 he moved to a cottage near Sutton Veny, where he entertained friends and his many godchildren, and studied the great-crested newts in his pond. He created a water garden for which he designed a bridge, and his taste in furniture, gardens and food was original and immaculate.

Cripps succeeded his father (who had only seven months before suceeded his brother) as 4th Baron in 1977.

He had intended to leave money for his friends to throw a party after his death. But when his doctor said he would be dead in a week, he decided to be present in person. The upshot was a series of lunches with Cripps attending in his wheelchair. The last was on June 28, only weeks before he died.

He is succeeded by his cousin Michael Leonard Seddon Cripps.

Lord Parmoor (Milo Cripps), 4th Baron, banker and antiquarian bookseller, was born on June 18, 1929. He died on August 12, 2008, aged 79