Is Olly Robbins the 'real' Brexit secretary?
What do we know about one of the best-known unknown people in Downing Street?
As a Whitehall mandarin who has spent years shunning the limelight, Oliver "Olly" Robbins is contemplating something of a personal failure.
One of the tallest men in the British establishment is developing - much to his irritation - an uncharacteristically high political profile.
Some Brexit supporters have the prime minister's chief adviser on Europe in their sights amid fears that the government may be shepherding Britain towards a gentle exit from the EU. One senior minister told Newsnight he believes that Olly Robbins regards Brexit as a crisis to be managed rather than an opportunity to be seized.
Leavers are suspicious of Mr Robbins because the man dubbed the "real Brexit secretary" wields immense power as, in the parlance of diplomacy, her EU "sherpa".
This role gives him a seat by Theresa May's side at all the main Brexit meetings in Downing Street and a berth in Brussels for the main day-to-day Brexit negotiations.
So just who is this Whitehall high-flyer who has, barring a run-in with the Guardian over the leaked Snowden files, largely remained in the shadows in his two decades as a civil servant?
Friends and critics say that the first quality that stands out about Mr Robbins, 42, is his immense brain. But he wears his intellect lightly and was a source of gallows humour in Downing Street during the fraught days of Gordon Brown's premiership.
Tom Fletcher, an Oxford contemporary who served beside Olly Robbins in Downing Street during three premierships, told Newsnight: "This is someone who can take a policy paper and distil it very, very fast and spot the three weaknesses.
"But he has always also had a certain amount of humour as well. When you are working somewhere like Downing Street you really need that. It is a tough job and he has got that resilience and calm under pressure which we always valued."
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Critics say that Mr Robbins is so driven he can perhaps be a little insensitive towards people below the prime ministerial circles which are now his natural milieu.
But these critics agree with his friends on one quality: his supreme mastery of the art of winning the confidence of prime ministers and cabinet secretaries in a career that has spanned the Treasury, Downing Street, the Home Office and the world of British intelligence.
Allies of four prime ministers - Tony Blair, Gordon Brown, David Cameron and Theresa May - all say Mr Robbins stood out among a competitive field of bright young civil servants. Lord O'Donnell, the former cabinet secretary, first spotted his talent when Robbins worked in the Blair Downing Street.
His two great patrons are the current Cabinet Secretary, Sir Jeremy Heywood, and Theresa May who was impressed by Mr Robbins when he held a senior Home Office post. Friends say he was one of the few officials who understood May's approach on immigration.
His reward came when Nick Timothy, Theresa May's former joint chief of staff, granted Mr Robbins the ability to walk into May's No 10 office for a chat on his own.
Chris Wilkins, Mrs May's former director of strategy, told Newsnight: "Olly was somebody who had the full trust of the prime minister, had the full trust of Jeremy Heywood as well and was able to own meetings and run meetings in a way that made the process very smooth and very effective."
Oxford provides a good place to understand the instincts of a man who will play such a central role in shaping Britain at a defining moment.
Mr Robbins followed the classic route of a senior mandarin by studying politics, philosophy and economics at the university in the 1990s. But he chose Hertford College, which has championed a more inclusive admissions policy since the mid 1960s, rather than one of Oxford's grander colleges.
Tom Fletcher said: "Even at university it was already clear that this was a guy who was going to make a success of whatever he did. It is fair to say he's the sort of person you'd be more likely to see in tweed than in a football kit."
Tom Fletcher and Olly Robbins formed part of a quartet of Hertford graduates who at one point controlled British intelligence at the heart of Whitehall.
The others were his patron, Sir Jeremy Heywood, and his closest Whitehall friend Ciaran Martin, now chief executive of the National Cyber Security Centre. It was an intelligence conspiracy that never was, according to the Hertford grouping.
One Tory Brexiteer who went to a top-tier Oxford college is dismissive of the Hertford circle. "They're all Commie geographers," the Tory told Newsnight.
Brexiteers were delighted when the Guido Fawkes website unearthed an Oxford article in which the young Olly Robbins wrote that the Soviet Union wasn't all bad.
Newsnight understands that David Davis, the actual Brexit secretary who is said to have something of a prickly relationship with Mr Robbins, has a habit of opening meetings with him by welcoming colleagues to the "Olly Robbins People's Soviet". Everyone reportedly has a chuckle at the Davis teasing.
But Mr Robbins is understood to be conscious of how some Leave ministers are wary of him. He worked hard to win Boris Johnson and Michael Gove over to the prime minister's EU speech in Florence last September, making changes on the way.
But in the tense week in December, when the phase-one Brexit deal appeared to be on the verge of collapse, there was some frustration in the Cabinet Office that those ministers were less supportive.
Chris Wilkins told Newsnight: "I think inevitably because of the role that Boris and Michael played during the Leave campaign clearly they are big figures who need to be part of this process and bought into it. From what I've seen, I think Olly deals with them and their offices very effectively."
So a consummate Whitehall operator, with experience in the smoke and mirrors world of intelligence, is guiding the Brexit process. Sadly for Olly Robbins this means leaving the shadows and becoming a reluctant public figure.