He might be known as the “Brains of Britain”, but heavyweight commercial silk Jonathan Sumption QC was lucky to get to the bar at all. Both of the chambers that had provided him with pupillage – 20 Essex Street (at the time 3 Essex Street) and Gordon Pollock QC’s magic circle set Essex Court (at the time 4 Essex Court) – rejected his tenancy applications out of hand. Sumption despaired until the efforts of Michael Mustill (now Lord Mustill QC) finally secured him a home at Brick Court, where he has remained to this day.

And how Brick Court has benefited. Without Mustill’s efforts the set would have lost out on one of the leading triumvirate of current practitioners at the bar. The other two members of the elite are Lord Grabiner QC at One Essex Court and Gordon Pollock QC at Essex Court. “I was a pupil of an awful lot of people because I found it very difficult to get a tenancy in chambers. Michael Mustill took time off to lobby for me at Brick Court. If he had not, I would probably have had to abandon my ambitions at the bar. Chambers are always reluctant to take on someone who has been a pupil elsewhere for 18 months,” says Sumption.

Despite such inauspicious beginnings and his famously unkempt appearance, Sumption’s reputation was soon established and his practice now covers a huge number of fields: commercial law, public law, general banking, civil fraud, financial services, insurance, media, energy, shipping and professional negligence.

Litigation partner Charles Plant at Herbert Smith says: “[Sumption] is my first choice on a wide range of commercial matters. His intellect is unsurpassed and he has the most incisive legal mind that I’ve encountered in over 30 years of practice. Couple that with a ferocious appetite for work and meticulous preparation – and unlike some of his peers he does not rely heavily on juniors – and you ge

t the best show in town.”

According to Sumption, though, it is luck that has been the main element behind his success. “Some [practitioners] have always been outstanding, but nobody has noticed. You need a lot of luck in this business. It’s not good enough to be first class, someone’s got to notice the fact,” he says. Thankfully he was noticed, because the prospect of a life of academia – his first-choice alternative career – was by that time already losing its appeal. He had already spent five years as a history don at Oxford University before falling prey to the allure of self-employment. He says: “I could see myself getting very fed up with academic life when I was in my mid-40s. I was constitutionally incapable of being employed. The bar seemed more interesting than any of the other prospects, except possibly the medical profession, which was far too difficult and long.”

One of the reasons for his success is that, unlike many practitioners who enjoy nothing more than becoming embroiled in intellectual debates over the finer points of black letter law, Sumption is keen to dismiss the mystique of his profession. “In most cases, 99 per cent of the facts are irrelevant, either legally or factually or both,” says Sumption. “The art of advocacy is to strip those away. When you’re down to the last 1 per cent, the answer should be obvious.”

This ruthless ability to wade through mountains of information led him to victory in the Equitable Life case at the House of Lords, where in the Court of Appeal Sumption once again came up against his old adversary Grabiner. Controversially, Grabiner was replaced with Elizabeth Gloster QC, a fellow tenant of One Essex Court, when the case went to the House of Lords. Sumption admits: “I did say some rude things about [Grabiner’s side’s] affidavits…”

However, Sumption is not about to embark on a character assassination of his great rival. Far from it. “The three of us [Pollock, Grabiner and Sumption] are together regarded as forensic thugs, so one might assume we are brutes. Pollock is in fact an extraordinarily sweet-natured man when you talk to him about something other than law. I would not say Grabiner is sweet. He would be most offended. But he is agreeable. He is an exceptionally amusing man and a kind one.”

According to Sumption, Equitable Life had no choice but to take the case to the Lords. “It was essential to test the policy once [Equitable Life] embarked upon [its policy], as it was a business question, although [the decision] must have cost them a great deal of goodwill,” he says. “They have one of the most demanding client bases in the market. A very high proportion of them are professional people such as solicitors and accountants, so if you’re going to find a group to quarrel with, that one doesn’t seem ideal.”

Sumption is an avid exponent of the virtues of the House of Lords and obviously revels in performing there. He says: “The House of Lords has been at a very high quality for a very long time. You get a good hearing and impressively reasoned decisions there.” This means, in his eyes at least, that he can win even when he loses. “In the South Australia Asset Management case, the House of Lords accepted my submissions on the law but then held that the facts of my client’s case were so disastrous that they lost even though my legal submissions were right,” he says. “So you know I go down as having lost that case, and quite rightly, because I did lose it. On the other hand, in the sense that matters, in the way that gives me satisfaction, I actually won it.”

Sumption, however, is rather less effusive about the workings of the Court of Appeal. He says: “It has become increasingly difficult to get a proper hearing of genuinely disputable issues in the Court of Appeal. I certainly think that in the last three years the Court of Appeal has been doing things in too much of a hurry, as a result of which it is not always identifying points that actually require a more careful approach.”

So what about the future? Sumption is 52, and if he is not going to go to the bench, what looms on the horizon? He hints that he could be persuaded to follow the path of Lord Grabiner. “In the extremely unlikely event of somebody asking me whether I’d accept a peerage, I honestly don’t know what I’d say. I can see the advantage of having some involvement in the political process without the awful grind of having to be elected.”

If that is part of the plan, then he may have to be less contrary with his politics. “I voted for Labour. I think they’ve proved to be a very competent government and impressive economic managers. But I’m not a natural supporter of theirs. I’m basically a Tory who votes Labour much of the time.”

However, his love of history may yet draw him back to the academic life he rejected 25 years ago. He is devoted to the subject. “I don’t love law but I enjoy practising it. I do love history,” he says. He owns 7,000 history books, has already spent nine years producing his volume one of the 100 Years War and a further eight years on volume two.

“The thing about this job is that you don’t need to give it up all in one go,” says Sumption. “I can see myself reaching a stage when, without actually retiring, I will practise less. Around 60 perhaps? I’d like to do more historical writing, make faster progress on the 100 Years War, review more books and accept invitations to do papers on historical subjects, whereas I rigidly refuse at the moment because I simply cannot combine it with legal practice.”

Sumption is self-evidently an astonishingly talented man. But surely he must have some faults? “I play the piano badly,” he concedes, although confesses that no one ever believes him. “As a result you get known for being an ace pianist and tremendously modest too. But I have to say that when I say that I play the piano badly, I really do mean it.”

So let’s set the record straight. Sumption is a great advocate but an awful pianist.