How bizarre that the British press, which has devoted millions of words to every twist and turn of Brexit, has yet to publish a single profile of Geoffrey Cox, the Attorney General. It is no exaggeration to say he could soon hold Theresa May’s fate in his hands, for Cabinet ministers no longer trust Downing Street to tell the truth and have said they must see Cox’s written opinion on the exact meaning of whatever deal she brings back from Brussels, before they accept or reject it.

And the Attorney General is a wonderfully vivid figure. Few Conservatives realised this until he turned out to be the “celebrity” speaker promised as the warm-up act for the Prime Minister at the party conference in Birmingham.

Instead of some ingratiating person from television, some bargain-basement version of a Hollywood star, we found ourselves confronted by a barrister who seemed to have stepped straight from the 1950s, a rotund yet authoritative orator with a rich, deep, clear, sonorous, well-modulated voice, marinated as it sounded in the finest Middle Temple wines, disdaining all latter-day nostrums about the art of advocacy.

His hand gestures were poor (one of them can be seen in the illustration accompanying this piece), but his speech, which can be listened to for pleasure, was a triumph. After touching on the “precious prize” of parliamentary sovereignty, Cox warned that “in the real world nothing so valuable is ever gained without sacrifice and compromise”, and went on:

“Since the 17th century the special genius of the British peoples has been the flexibility to find compromises and constitutional arrangements that may not possess ideological or theoretical purity, but which work.”

The last three words were spoken with especial trenchancy. Here, it might be thought, was a speaker preparing us for some kind of surrender, from which we were to be distracted by the sublime passage from Milton’s Areopagitica in his peroration:

“Methinks I see in my mind a noble and puissant Nation rousing herself like a strong man after sleep, and shaking her invincible locks: Methinks I see her as an Eagle muing her mighty youth, and kindling her undazl’d eyes at the full midday beam.”

When did one last hear anything half so fine at the end of a party conference speech? “Muing”, by the way, means “moulting”, so by extension “renewing”.

But Cox is not afraid to be critical when he considers it necessary. At the Cabinet meeting of 16th October, he is reported to have said that “any Northern Ireland-only arrangements for customs after Brexit could mean the province was ‘torn out of the UK’ and leave it ‘controlled by the EU’.”

Ministers are furious they were misled by Downing Street officials who in December downplayed the significance of the Irish backstop, and they look to Cox to save them from repeating that error. Michael Gove apparently told the Cabinet: “Fool me once, shame on you; fool me twice, shame on me.”

The night before this Cabinet, eight ministers, including Cox, Gove, Dominic Raab, Jeremy Hunt, Penny Mordaunt, Liz Truss and Chris Grayling, convened over pizza in Andrea Leadsom’s office to discuss their concerns about May’s approach.

And at the Cabinet held a week later, Cox observed, as James Forsyth reported for The Spectator, that the backstop would be like being stuck in Dante’s first circle of hell:

“Geoffrey Cox…was the bluntest. He warned the Cabinet that the choice before them was between a backstop that as currently proposed the UK—or at least part of it—couldn’t get out of, no deal or repudiating the backstop. Very soon, Theresa May and the Cabinet is going to have to decide which of these is the lesser evil.”

There has been talk of Parliament voting down May’s Brexit deal and seeking to take control of the process. Before that happens, it appears the Cabinet seeks to take control, and has perhaps already done so.

And since most Cabinet ministers find their heads swim as they contemplate the mysteries of the Irish backstop (a feeling with which many of us will sympathise), they look to Cox to explain, with complete honesty and no bias or topspin (as one minister put it to me yesterday), the full legal and constitutional implications of the terms on which Britain is leaving the European Union.

How can Cox, who was only appointed Attorney General in July, have attained so rapidly such an influential position?

The answer is that his reputation for giving independent advice on complicated and contentious legal matters, often involving international law and the negotiation of treaties, was not acquired in the last four months, but over a career of 36 years at the English bar.

He is that old-fashioned figure, the lawyer-politician, who combines two complementary professions, practising one in the morning and the other in the afternoon and evening. Such people were needed in the 17th century and are needed now, not that one would guess it from the meagre and repetitive coverage of Cox’s legal career in the media.

In 2014, he earned a total of £820,867 as a barrister – a figure almost invariably reported with much tut-tutting, as being the ill-gotten gains from a career evidently spent moonlighting from his proper job as an MP, which he must be neglecting. Paul Goodman pointed out, on ConHome, how misguided this attitude was:

“The problem with Parliament isn’t that there are too many Geoffrey Coxes, but too few.  Able people are sniffing the wind.  They look at the Commons, with its declaration requirements for outside earnings (which are designed to discourage them), IPSA, and media intrusion (in which families are fair game), and decide it’s not for them.”

Cox carries authority because he reached, on merit, the top in a profession where success does not depend on currying favour with politicians, or indeed with the wider public. There is an undertone of traditional bloody-mindedness in his demeanour.

The downside of this could be an intolerable pomposity. But as far as one can see, he knows when to shut up. After his party conference speech, which he described as “a flash in the pan”, he could have become promiscuous, and given interviews all over the place, but he confined himself to speaking quite briefly and uninformatively to The Times.

He was born in Wiltshire in 1960, the son of a soldier, and educated at King’s School, Taunton, and at Downing College, Cambridge, where he read English and Law, He was called to the Bar in 1982, and in 1996 co-founded Thomas More Chambers in Lincoln’s Inn Fields, which in more recent times has been complemented by Thomas More International, based in Mauritius (he was pupil master to a Mauritian prime minister) and Dubai.

Cox first stood for Parliament in 2001 in the vast, rural constituency of Torridge and West Devon, and lost to the Liberal Democrat. In 2005, he managed to reverse this verdict, and won by 3,236, a majority which by 2017 had increased to 20,686, so his constituents do not appear to harbour an invincible prejudice against him for having continued his career at the bar – something which in any case stopped when he became Attorney General.

On his website, he emphasises his local connections:

“Geoffrey lives in West Devon, near Tavistock, with his wife, Jeanie and his family. They have a daughter and two sons, Charlotte, James and Jonathan who attended the local village school. Geoffrey was born and brought up in the West Country…and his family have been Devonians for generations. His brother is a local solicitor. Geoffrey is strongly involved in the local community, and among other posts, is President of the Tavistock Football Club and a Vice President of the North Devon Hospice, which he named as his MP’s Charity.”

But his legal connections are what interest the wider world. Philippe Sands QC, Professor of Law at University College London and by no means a Conservative, describes Cox in the following terms:

“A grown-up lawyer with experience of life and the law, thoroughly independent and fearless in the best traditions of the English bar. I was much reassured by his appointment, relieved that there will be at least one grown up at the Cabinet table when the hard and painful legal realities of Brexit are addressed.”

Andrew Mitchell, former International Development Secretary and Chief Whip, says of Cox:

“He’s a huge improvement. He looks and sounds like a proper, old-fashioned Attorney General and we are already calling him Sir Geoffrey. He has real presence and authority and we have not had that since Dominic Grieve. Everyone knows he will give his advice without fear or favour to the Prime Minister and the Government – unlike some of his predecessors, who have basically served up what the Prime Minister wanted to hear.”

In July, when David Davis and Boris Johnson resigned, Cox came on board and steadied the ship by defending the Chequers deal. What he will do now is less clear. As a pupil master and leading counsel, he would often take his juniors to the Savoy for tea, where they could digest the day’s play as well as the cakes. In more recent times, he has done the same for parliamentary colleagues who want to explore the intricacies of Brexit.

But he has not volunteered that kind of service to the media. He instead gave an interview to Prep Radio, at Mount Kelly School in Tavistock, where he had himself been a parent when the prep school was called Mount House. When asked which MPs he had been impressed by, he named the late Jo Cox, Jesse Norman, whom he called “quite brilliant”, and Frank Field.

Asked which three people, dead or alive, he would invite to dinner, he named D.H.Lawrence, T.S.Eliot and “Frank Raymond Leavis” – F.R.Leavis, the great English critic at his old Cambridge college. All are more modern choices than might have been expected.

And asked what he would like to have been if he had not been a lawyer and a politician, he replied that he would like to have been a poet, “but I’m not good enough”. In response to the question of his greatest achievement, he replied “thirty-five years of marriage – well it’s really my wife’s achievement, not mine”.

The best piece of advice he had ever been given was “don’t go into the Church”, though he spoke with affection of attending the Sunday morning services at Mount House.

These answers suggest the possession of a hinterland.They do not, however, indicate what he is going to say about the Brexit deal. But just by being there, he helps to impose Cabinet discipline on the Prime Minister, and makes a sloppy Brexit less likely.