Jonathan Sumption: Donnish but deadly

One of the most brilliant QCs of his generation, he is centre stage in a legal drama pitting two Russian oligarchs against each other – and poised to join the elite club that is the Supreme Court

Brick Court is one of the most successful commercial barristers' chambers in the country.

Its 75 silks and juniors comprise some of the leading advocates of their generation and many of its previous members have gone on to become senior judges. In the early 1980s, its most formidable clerk, a man of trenchant views and long experience, observed of Jonathan Sumption, then a young barrister, that he had never seen a more obvious candidate for the House of Lords.

Soon this prediction will come true: within a few months, Sumption will be gazetted with a life peerage and take up a new post as one of the 12 justices of the Supreme Court. This leap from the bar to the highest court in the land is almost unprecedented.

In the meantime, Sumption is very much in the spotlight. Every day the newspapers carry reports of the proceedings in the new Rolls Building of the Commercial Court. Two London-based Russian oligarchs, Boris Berezovsky and Roman Abramovich, are head to head before an English judge, seeking judgment on share deals done in the wild east of Russia of the 1980s worth billions of dollars. It's been a picturesque scene with expensive lawyers, taciturn bodyguards and glamorous consorts.

And Sumption, as Abramovich's brief, has been at the forefront, cross-examining Berezovsky for the past fortnight. The trial is expected to last at least another 10 weeks. However it ends, it will form a suitably impressive conclusion to one of the most remarkable – and lucrative – careers at the bar of modern times, played out in high-profile, high-stakes cases for clients who have included the British government, Alastair Campbell and the Queen.

Campbell's diaries characterise Sumption as a man with a brain the size of the planet. This fearsome intelligence is his most outstanding quality allied to prodigious energy. In person he has a slight air of donnish dishevelment and a fizz of nervous energy.

Sumption did not intend to become a lawyer. He was educated at Eton and then Magdalen College, Oxford, where he took a first in history in 1970 and stayed on as a tutor, specialising in the medieval period. His first book on pilgrimage in the Middle Ages was published in 1974.

He has been forthright about his reasons for leaving academic life. "It is extraordinarily badly paid, and in the long run this will be a disaster. The quality of people going into teaching and research is not what it once was. If I'd been earning double the £2,500 I was in 1971, I would have been quite happy remaining."

For some time he considered politics as an alternative career. Though he voted Labour in the 1970s, he was also close to the Conservative politician Sir Keith Joseph, in the 1970s when Joseph was assembling the intellectual framework for what later become known as Thatcherism.

They wrote a book together about equality, the theme of which was that no convincing arguments for an equal society have ever been advanced, that no such society has ever been successfully created. Politics was discarded, however, because of the "demands it makes on one's time. There is also a very narrow apex. There is not much of any interest below the top". In fact, his politics have always been mixed. In 2000 he said that "basically I'm a Tory who votes Labour much of the time".

Eventually law seemed to offer the best opportunity for an intellectually stimulating occupation with the opportunity to make a reasonable living. He joined the bar in 1975 and rapidly made a name for himself in a series of commercial cases, becoming a QC in 1986.

In addition to the commercial work he has been employed by the government. In 2000 he advised Jack Straw, then Home Secretary, during the attempted extradition of General Pinochet from the UK to face criminal charges in Spain. He was Alastair Campbell's brief during the 2003 Hutton inquiry. In 2005 he defended the then Transport Secretary Stephen Byers in the largest class action ever brought in the UK by disgruntled shareholders over the controversial nationalisation of Railtrack.

Fellow silks, not often noted for unselfish admiration of their colleagues, admit that he is a superb courtroom performer, with an unrivalled ability to maintain a sustained focus on the essential elements of a case, and capable of devastating cross-examination.

Their appreciation also extended to the fees he could command. From at least the middle of the 1990s, Sumption has belonged to the financial elite of the bar, earning more than a million pounds a year and sometimes much more. His fee from Abramovich was initially rumoured to be £10m, but this has been firmly denied by Brick Court – £3m may be closer.

He enjoys the money. "The trouble with a large income is that it leads to extravagant tastes, and you don't want to give those up." He is married with three children, all privately educated. He is devoted to opera (and is a governor of the Royal Academy of Music). He owns property in London and France. Alastair Campbell noted in his diary: "I don't know whether it was a joke or not but according to others he owned a village somewhere in the south-west of France."

One use he makes of his wealth is to fund a parallel career as an independent historian. As a self-employed QC, he dictates his own working hours. "At the bar you can take holidays when and for as long as you wish, so long as you realise that holidays make losses. I can also work more productively than any academic because of my large personal library – about 7,000 volumes on the Hundred Years War alone – which I can only afford because I'm a lawyer. The other part of the secret is to neglect one's family, and rely on their infinite tolerance."

Since the late 1990s he has been engaged on a vast narrative history of the Hundred Years War, three volumes of which have now appeared to critical acclaim. There will be another two: the fourth covering 1399 to 1422 is intended to appear in 2015, the 600th anniversary of the English victory at Agincourt.

What can we expect from Lord Sumption when arrives at the Supreme Court? Naturally many in the legal profession are resentful at such a rapid promotion – the last such was in 1949 – but there is also a feeling that he will bring a considerable and necessary boost of intellectual firepower to the roster of our senior judges, depleted by death and retirement over the past few years.

Few would have expected Sumption to have fared well, or found much enjoyment, as an everyday High Court judge. In an interview in Prospect earlier this year after the announcement of his appointment, he was asked what his judicial philosophy would be: "You cannot relate the political sympathies of judges to the way they decide cases. A judge ought to have a healthy balance of respect for the governmental function combined with scepticism about the motives of particular ministers or officials."

He has expressed concern about the reach of the European Court of Human Rights (ECHR). Our judges are obliged to "take account of" the decisions of the Strasbourg court, but there is disagreement over what exactly that means. Sumption believes the margin of appreciation – the amount of discretion that Strasbourg allows contracting states – is "absurdly and excessively narrow".

Supreme Court judges are obliged to retire at 70. This means Jonathan Sumption now has seven years to bring distinction to his latest career. Given his energy and intelligence, that should be more than enough.

A life in brief

Born: Jonathan Philip Chadwick Sumption, 9 December 1948.

Family: The son of Anthony, a submarine crew member turned barrister, and Hilda Hedigan. He is married to Teresa Sumption, has a son and two daughters.

Education: Attended Eton then Magdalen College, Oxford, where he graduated with first-class honours in history in 1970.

Career: After being called to the bar at Inner Temple in 1975, he became a Queen's Council in 1986 and a Bencher in 1991. He is joint head of Brick Court Chambers. Appointed to the UK Supreme Court in 2011. He has written numerous books on history and is a governor of the Royal Academy of Music.

He says: "It's an interesting intellectual exercise debating points of policy with highly intelligent people under ground rules which prevent you from evading the issue as one might over a dinner table."

They say: "He's a very clever person, a very strong advocate and extraordinarily hard-working. If you're against him, you know it's going to be a serious experience: he's a formidable opponent." Lord Grabiner QC, his rival in many cases.