Rupert Hambro, who has died aged 77, was a stylish financial entrepreneur in the fifth generation of one of the City’s most illustrious banking dynasty.

Hambro had barely passed his 40th birthday in 1983 when he succeeded his cousin Charlie (later Lord Hambro) as chairman of Hambros Bank, founded in London in 1839 by their forebear Carl Joachim Hambro, who came from a merchant family in Copenhagen.

In common with other family-led merchant banking houses, Hambros faced the dilemma of the City’s impending “Big Bang” reforms that offered expensive new opportunities in the securities markets, and heightened competition on all fronts.

The bank’s more cautious directors were disinclined to make any major move beyond buying a stake in a stockbroker, Strauss Turnbull; though its capital had been bolstered by the successful sale of its life assurance arm, it was hampered by low profits on its traditional lending and past losses on Norwegian shipping and North American oil and gas ventures.

Rupert and his younger brothers Richard and James, frustrated at having their family fortune tied into a business they felt they could not steer in more promising directions, resolved the internal tensions in 1986 by leaving – with their father Jocelyn, the bank’s elder statesman – to form their own business, J O Hambro & Co.

Moving to rented offices in Threadneedle Street, they found no furnishings other than telephones on the floor. Rupert called his friend Jennifer D’Abo, owner of Rymans stationery chain, and said: “Bit of a problem here … we haven’t a desk, a chair, paper, pencils, rubbers, paper clips, anything.” D’Abo arrived by lunchtime with everything in a van, and the following day a friend rang to ask his advice on a deal, “ … and that sort of gave one a feeling that maybe the world was going to be all right.”

The boutique operation, specialising in investment management and corporate advice, suited Rupert Hambro much better than the larger bank – where, he once observed, the dealmakers naturally rose to the top but then found themselves worrying about “the carpets and the nightwatchman’s salary” while the customers asked: “Where are you?”

With his brothers leading the investment side, Rupert focused on mergers and acquisitions, forming a partnership in 1988 with another high-profile City player, George Magan. As Hambro Magan their roll-call of major transactions included the sale of Morgan Grenfell to Deutsche Bank, of Warburgs to Swiss Bank and of Jaguar to Ford – and finally the sale of their own firm to NatWest in 1996.

Energetic, gregarious, always entertaining company, Hambro had a roving eye for business opportunities but little time for detail: one profile praised his “cavalier dash”.

Alongside a huge portfolio of boardroom and committee roles, a knack for befriending talented people drew him towards the venture-capital arena, where he invested with Jennifer D’Abo’s son Joel Cadbury in the Groucho Club and Vingt-Quatre, London’s first 24-hour restaurant, and was an early backer of the Sipsmiths gin brand that was eventually sold to Japanese investors for £50 million.

In his mid-seventies, despite health problems, Hambro created a new partnership with a financier in his thirties, Dominic Perks, to back start-ups ranging from a dry-cleaning app for busy people to a Muslim dating site and a Warwickshire craft brewery.

He stayed active, he told an interviewer, because he enjoyed “bringing a bit of grey hair” to young entrepreneurs. Others may suffer from Rectory Syndrome – the aspiration to do no more than buy a country home and ease back – he observed, but, he said, “I’ve worked all my life and I’m not ready for the rectory.”

Rupert Nicholas Hambro was born on June 27 1943, the eldest son of Jocelyn Hambro and his wife Silvia, née Muir. After winning an MC with the Coldstream Guards in Normandy in 1944, Jocelyn lost a leg when a German shell hit an officers’ conference – later remarking “What a day to be shot, August the 12th”– but went on to run Hambros Bank in the 1960s and early 1970s with what his obituarist called “a gambler’s instinct for risk” combined with “an urbane, insouciant style” – traits which Rupert amply inherited.

Rupert was educated at Eton and the University of Aix-en-Provence, where he learnt French and studied International Law. He then embarked on (but only partially completed) accountancy training with the firm of Peat Marwick Mitchell in London and Manchester before joining Hambros Bank in 1964 and spending time on attachments in Copenhagen, Geneva and Canada, where the family had mining interests.

In London he specialised in the fast-growing Eurobond business, in which Hambros built a strong position on behalf of its Scandinavian client base, becoming a director of the bank in 1969 and deputy chairman in 1980. One of the youngest of the City’s top echelon, he was ticked off by the Governor for attending an emergency meeting at the Bank of England (concerning the collapse of the bullion bank Johnson Matthey) in jeans and pink socks.

He was also chairman of the Association of International Bond Dealers – on one occasion presiding over a gathering of 2,000 members in Venice, whose mayor told him he would be held personally responsible for any damage.

Among many other corporate appointments, Hambro was a director of the Telegraph Group, the South Africa mining giant Anglo-American and the Sedgwick insurance group.

He was chairman of Hamleys, the Regent Street toy shop which he bought with institutional backing and led to a public listing in 1994, and of Wilton’s in St James’s – which his grandfather Olaf had famously bought in 1942 from its previous proprietor, Mrs Bessie Leal, after dining at the bar and telling her to “put the restaurant on the bill”.

He was also a director of Racecourse Holdings Trust, which owned courses and training grounds on behalf of the Jockey Club, and of Chatsworth House Trust.

Beyond business, Rupert Hambro’s commitments ranged from boys’ clubs in the East End to trusteeships of the Wallace Collection and Chiswick House. He chaired the governors of the Museum of London, the development board of London Zoo and the council of the University of Bath at Swindon, and was president of the British Association of Adoption and Fostering.

As a popular prime warden of the Goldsmiths’ Company in 2009 and 2010, he was remembered for arriving at livery events on his motor scooter.

Rupert Hambro and his American-born wife Robin, a former fashion journalist, maintained a tireless social whirl on both sides of the Atlantic and a happy family life.

In a last interview, in April 2020, he revealed that the four people he would most like to have invited to dinner were Marilyn Monroe, Albert Camus, the Hong Kong tycoon Li Ka-shing and the jeweller Theo Fennell, whose business he part-owned; in a biopic he would like to have been played by Jack Nicholson. His lockdown advice to the young was “Hang in there.”

He was appointed CBE in 2014. He married Mary Robinson Butler, née Boyer, in 1970; she survives him with their son and daughter.

Rupert Hambro, born June 27 1943, died February 19 2021