At every European summit, including no doubt the one which opens today, Ed Llewellyn can be seen at David Cameron’s side, or else standing just behind him.

The proximity of this neat, bespectacled, well-mannered figure rouses in some Eurosceptics deep suspicion. They point out that before becoming, in 2005, Cameron’s chief of staff, Llewellyn worked in a similar capacity not just for Paddy Ashdown, but much worse, for Chris Patten.

They also observe that Llewellyn is now immersed, along with Cameron, in the renegotiation of Britain’s relationship with the European Union.

So for the kind of Eurosceptic who is ready, on the slightest provocation, to suspect a sell-out, Llewellyn’s involvement looks like confirmation that the Prime Minister is not intent on obtaining serious concessions from Brussels.

Douglas Carswell’s defection last year from the Conservative Party to UKIP appears to have been triggered by the sight of Llewellyn at a Königswinter conference in Cambridge. For according to Carswell, Llewellyn and other senior Whitehall figures were “smirkingly, eyeball-rollingly contemptuous” of the idea of making changes to the European treaties, while they were clearly on the same wavelength as the senior German policy-makers at the conference.

Eurosceptics of a Carswellian disposition will not be comforted to learn that Cameron’s nickname for Llewellyn is “the pocket Talleyrand”.

For was not Talleyrand (1754-1838) a brilliant but notoriously disloyal figure, with a gift for choosing the opportune moment to abandon whichever regime he happened to be serving?

For Cameron, that will be part of the joke of using the term. For while Llewellyn possesses a comprehensive knowledge of European diplomacy, he is also, as several people who know him well emphasised, unshakeably loyal to whoever he is working for.

He has served Cameron for a decade with self-effacing discretion. If you google his name, you discover next to nothing about him: just the repetition of the same bare facts.

No profile of him seems to have been written: a singular achievement when one considers he is one of the most influential men in the country.

In the last Parliament, Llewellyn nevertheless attracted, from time to time, heavy criticism from Tories who thought the Downing Street machine was hopelessly underpowered.

Special advisers in several departments accused him of being too well-disposed towards the Liberal Democrats.

After all, Llewellyn had not only worked, in Bosnia, for Ashdown, a former Lib Dem leader, but is on friendly terms, since working in Brussels for Patten, with Miriam Gonzalez Durantez, wife of the current Lib Dem leader, Nick Clegg.

Just before writing this piece, I bumped into Tim Shipman, the Sunday Times’s political editor. He reminded me of a blog he wrote in the summer of 2012 for the Daily Mail, describing the discontent then directed against Llewellyn:

“Several Tory spads have told me they like to work on things in their departments because once policies get into Mr Llewellyn’s clutches, they fear they will be watered down out of all recognition through exposure to Lib Dem doubts. Another No 10 source told me this week: ‘Ed thinks his main role is to hold the coalition together’… Many date the lack of a strong figure to grip policy and drive things through to the departure of communications chief Andy Coulson, though he was never that engaged in policy development. Steve Hilton, also departed, had big ideas and the ear of the PM but not the patience and guile to bend the civil service to his whim. What Tory MPs and aides seem to want is an amalgam of Hilton and Coulson in Llewellyn’s job. ‘We don’t need dozens of people, we need one strongman and we need a narrative,’ said a senior Tory source. ‘There hasn’t been an arsekicker since Andy left and we arguably haven’t had a strategy since then either. Steve was a big personality but he wasn’t a conventional strongman. What we need is Leo McGarry [the fictional White House chief of staff in The West Wing], what we’ve got is Leo Sayer.’”

Dominic Cummings, who for most of the last Parliament was Michael Gove’s spad, recently put these criticisms in particularly vivid form, dismissing Llewellyn as “a classic third-rate suck-up-kick-down sycophant presiding over a shambolic court”.

But these attacks look harder to sustain when one considers what happened to the Lib Dems at the last general election. Cameron confounded expectations, and won a slim overall majority, by almost annihilating his junior partners, who now have only eight MPs.

It appears that holding the coalition together for the whole of the last Parliament has worked rather well for the Conservatives. Nor is this something an “arsekicker” chief of staff would have been likely to achieve, or even to regard as a priority.

The Lib Dems were killed by kindness. The courtesy, consideration, reliability and civilised behaviour shown towards them by Cameron, Llewellyn, and others, lured them into a coalition, and never provided them with an excuse to walk out.

Here is a vindication of the Cameron-Llewellyn style of government. A key point to understand is that good manners do not necessarily denote weakness: they can be a way of getting other people to do what you want.

The Cameron-Llewellyn Cabinets have been, by normal standards, astonishingly durable. In a break with tradition, ministers have been placed in charge of departments of which they already have some knowledge, and have been left there for long enough to see through considerable reforms.

One of Llewellyn’s closest colleagues says of him:

“He’s very courageous. He has the courage of a lion. He has absolutely no fear at all. It doesn’t matter who he’s dealing with. He is tactful and polite but utterly resolute. You know where you are with him. But he’s extremely good at making people think the thing he’s trying to get is something they want. He operates on the principle that you can get almost anything done as long as you don’t mind who takes the credit for it.”

Julian Astle, a Lib Dem who from 2002-05 worked with Llewellyn for Ashdown in Sarajevo, has said of him:

“Not once while I worked with him did he shy away from bringing the boss bad news. Unlike a good many political advisors, Ed was unfailingly polite and respectful, but he never flinched; he was always prepared to tell Ashdown what he least wanted to hear when he knew he needed to hear it. There were plenty of ‘yes men’ in the organisation but Llewellyn wasn’t one of them.”

Llewellyn is the son of a naval officer who went to Dartmouth at the age of 13 and served for over 40 years. One may guess that this services background helped to form Llewellyn’s undemonstrative sense of duty and teamwork. His mother, who died when he was only 11, had always wanted him to go to Eton, which he did. At New College Oxford he read modern languages, was president of the JCR, and was known as Roddy, after the much more famous Llewellyn who was a friend of Princess Margaret.

Even before going to university, he had worked, in 1985, as a library boy at the Conservative Research Department (CRD), where he helped the deputy director, Alistair B. Cooke (now Lord Lexden), to compile the first volume of Margaret Thatcher’s speeches to be published, on defence and foreign affairs.

In 1988, Llewellyn became, as Europe desk officer, a full member of CRD, whose director, Robin Harris, was an exacting taskmaster and a fierce supporter of Mrs Thatcher. Lexden recalls:

“He won R. Harris’s full approval. Here is a man who from the start knew how to deal with difficult and demanding people like Harris and me. And he was swiftly on Mrs T’s approved list too as a mine of information on every aspect of European affairs. A little man (“little Edward” affectionately in those years), he went around with a large suitcase stuffed with the facts and figures for which she had of course an inexhaustible appetite.”

Here too, Llewellyn became friends with Cameron, who joined CRD soon afterwards, initially as desk officer for trade and industry. The Government’s professionalism can be traced to this institution, where they and others, including Oliver Letwin and George Osborne, worked at a young age for senior ministers and learned how politics works.

Jonathan Hill started out in CRD, went to work for John Major at Number Ten, and is now a European Commissioner. He recalled in an amusing interview with ConHome the part played by Llewellyn in the victorious 1992 general election campaign, and especially in Major’s rowdy, chaotic and highly successful soapbox appearances:

ConHome: “I saw that Ed Llewellyn had to hold the loudhailer during the campaign.”

Hill: “He didn’t have to. He volunteered. He loved the melée. He was always in the thick of it, Ed. Or Egg, as he became known, not very originally.”

ConHome: “So he got hit by lots of eggs.”

Hill: “Lots of eggs.”

ConHome: “Did you get hit by eggs?”

Hill [laughs]: “Of course not. I was cowering behind the detectives. It was mainly Ed and the Prime Minister. And Norman Fowler. Whenever we were egged, I tried to claim they weren’t throwing eggs at the Prime Minister, it was Norman Fowler who was the real target.”

This casts Llewellyn the foreign policy expert and chief of staff in a rather different light, as a man who relishes street politics.

Patten, who as Party Chairman had helped to mastermind the campaign, lost his own seat, in Bath, and went off to be the last Governor of Hong Kong. He describes Llewellyn, whom he took with him, as “impossibly decent…very diligent…[with] extremely good political judgment” (a verdict quoted in Michael Ashcroft and Isabel Oakeshott’s Call Me Dave).

Thatcherites tend to dismiss Patten as insanely favourable towards the EU. I am not sure this is right: I recall attending a conference with him a few years ago in Cracow at which he opposed, with staunchly Eurosceptic arguments, Polish policy-makers who were determined at the first possible opportunity to join the euro.

Within a few months, the victory of 1992 turned to ashes, with John Major’s Government humiliated by the ejection on Black Wednesday of the pound from the Exchange Rate Mechanism, which Cameron witnessed at the side of the embattled and humiliated Chancellor, Norman Lamont.

The party descended into civil war on the European issue, with Major at the mercy of the “bastards”: the band of rebels who could at any moment make his life a complete misery.

Cameron and Llewellyn will be acutely aware that a similar collapse in the Government’s authority could happen now, with an unexpected election victory soon vitiated by in-fighting.

Their EU policy has to be calculated to avoid, or give the best chance of avoiding, that disaster. Hence the Bloomberg speech in January 2013, in which Llewellyn was heavily involved, and in which Cameron in effect said to his backbench Eurosceptics: “OK, you’re demanding a referendum on our membership of the EU, and you can have one. But I intend to win it, by getting the British people to vote to stay inside a reformed Europe.”

To concede the referendum was a sign of weakness, but was the only way to keep the party united. Just as much of Llewellyn’s time in the last Parliament was spent devising the compromises which kept the alliance with the Lib Dems in mostly good health, so now he has to devise the compromises which maintain the Conservative Party’s own internal coalition.

Along with the Chief Whip, and Cameron’s parliamentary private secretary, he helps to absorb innumerable complaints, concerns, and expressions of hope and fear by Conservative MPs, and to filter these through to the Prime Minister. The people he deals with, and manages to calm down, know that when he speaks, he speaks for Cameron. If this were not true, there would be no point in talking to Llewellyn.

One should not, however, imagine a state of perpetual and idyllic harmony between the two men. It is said that when Llewellyn got engaged to be married to the Frenchwoman who is now his wife, and with whom he has two small children, he did not at first tell Cameron about the forthcoming wedding, but broke the news during a car journey on which he informed his boss that he would be taking a week off in order to get married.

Cameron took the news badly, but then wrote a paean of praise to Llewellyn which was read out by Patten at the wedding.

One of Cameron’s most powerful, though least observed, ways of controlling the parliamentary party is through the distribution of patronage, and especially of jobs: a task at which Llewellyn is brilliant. Only those who remain helpful during the European renegotiation can hope to be given jobs in the reshuffle which will follow its completion.

And then there will be the merits, or demerits, of whatever deal is reached, or not reached. Here Llewellyn’s contacts with his opposite numbers in the chancelleries of Europe, notably the Germans, could be of great importance. There is talk of a dirty deal with the Poles, where we would look with favour on their coal, while they would become a bit more understanding of our worries about immigration.

Even Cameron and Llewellyn are unlikely to know quite what concessions they will be able to get in the wearisome horse-trading which lies ahead. But those who are Outers at all costs are right to be suspicious of Llewellyn, for if anyone can help the Prime Minister to get a saleable deal, it is surely his chief of staff.