Boris Johnson will, I believe, vote to remain in the European Union. He is not yet ready to admit this: indeed, has two strong motives to avoid admitting it.

One of his strengths, both as politician and as journalist, is the lightning speed with which he reacts to a change in the story. If something goes wrong with David Cameron’s EU renegotiation, Boris wishes to be free to react accordingly.

He cannot bear the thought of giving up this freedom of manoeuvre and becoming a mere subordinate cog in someone else’s system. His column in Monday’s Telegraph, in which he asserted that the arguments for remaining and leaving “are as finely balanced as they have ever been”, should be understood in that light.

Boris was not, as some observers imagined, nailing his colours to the fence. He was covering a retreat: for his second pressing need is to let his Eurosceptic admirers down gently, by making a great show of demanding extra concessions from the EU, in order, later on, to justify voting to stay within it.

My colleague Mark Wallace immediately pointed out that “the disappointment should he eventually back Remain will alienate people who might otherwise have supported him” for the Tory leadership.

On Tuesday’s Daily Politics, Jacob Rees-Mogg issued a sterner warning:

“If the great Mayor of London is still making up his mind we wait to see which way he jumps. But if he jumps to stay in his chances of getting the leadership vanish because then he offers nothing against George Osborne and all the others who stay in.” 

This kind of warning gives Boris every incentive to veil his intentions for as long as he can, and to sound as Eurosceptic as possible. But unlike Rees-Mogg, I do not see how the Mayor can end up on the Eurosceptic side.

For the avoidance of doubt, I should state that Boris gave me no steer of any kind before I wrote this article. My purpose is to argue, as his biographer, that he is not by temperament an Outer, and would find it immensely difficult to throw in his lot with them.

True Eurosceptics do not agree with him that the arguments “are as finely balanced as they have ever been”. Parliamentary sovereignty is for them so valuable that it far outweighs whatever advantages we may derive from EU membership.

The word “sovereignty” is often, one has to admit, on Boris’s lips. In an ingenious passage in his party conference speech, he led on from some remarks about “dear Jezza … wondering whether to sing the national anthem”, to the Queen and “the ideas that she incarnates of our democracy and of the sovereignty of the Crown in Parliament”.

This last expression sounded reassuringly traditional. But in the many millions of words he has written and spoken, Boris has never taken the stern, unbending view of sovereignty which was expounded by Enoch Powell, and is held by Powell’s successors on the Tory benches.

As Boris cheerfully admitted, when I interviewed him on this subject just over three years ago, he has always been seen by hardline Eurosceptics as “incorrigibly wet”.

His position is closer to Cameron’s. Boris too wants to find a middle way, so we can have our cake and eat it. That may sound an implausible prospectus, but is one often offered by democratic leaders, and has generally characterised the British approach to the EU.

The last Tory Prime Minister, John Major, who at Maastricht achieved his own version of the middle way, then suffered so grievously at the hands of Eurosceptic Conservative MPs that in 1995 he challenged them to “Put up or shut up”. John Redwood accepted the invitation, and was photographed at his campaign launch with a bizarre group of supporters, including Tony Marlow in a stripy blazer, reminiscent (as Geoffrey Wheatcroft remarked in The Strange Death of Tory England) of “a theatrical party in Maidenhead”.

The truth is that Boris, although on friendly terms with many Eurosceptic Tories, cannot be said to be spiritually at one with them. Owen Paterson, Iain Duncan Smith, Peter Lilley, Bill Cash, Bernard Jenkin, Liam Fox, David Davis, Jacob Rees-Mogg, John Whittingdale, Chris Grayling and Steve Baker all possess, on the European issue, a more inflexible attachment to principle than characterises Boris.

William Hague used to belong to, indeed led, that group, but somehow acquired, during his time at the Foreign Office, a more worldly outlook, as has his successor, Philip Hammond.

The Eurosceptics are in desperate need of a leader who can unify them and present their case to the wider public. Neither Theresa May nor Michael Gove has shown any eagerness to volunteer for the role, which when one takes UKIP’s worsening internal dissensions into account, looks even more difficult.

If Boris were himself a true Eurosceptic, he could undoubtedly take it on. Indeed, the likelihood is that he would already be doing it, as Andrew Roberts urged him as long ago as May 2015.

But for Boris to pretend to think that Britain would be better off out would be a recipe for disaster.

That would be rather like trying to write a Jeffrey Archer novel while believing the way Archer writes novels is all wrong. At best, one produces a parody, but it is actually quite difficult after about three pages to keep going at all.

Euroscepticism is a harder cause to represent in a united way than one might think. Its adherents often disagree among themselves about the whereabouts of the last ditch which they are pledged to defend.

As Powell found to his dismay, pure Euroscepticism seldom attracts enough votes, and restating it in more and more vehement terms does not do the trick either. On 9 July 1976 – just over a year after Harold Wilson’s referendum on our membership of the European Economic Community – he declared in a speech at Bromley Chamber of Commerce:

“It is the nation that is dying, it is dying politically – or rather, perhaps, it is committing suicide politically – and the mark of death upon it is that it has lost the will to live.”

Even most Eurosceptics would now say this sounds a bit too pessimistic. The nation has proved more flexible and resilient than Enoch expected. Forty years on, we are in many ways a more confident nation than we were in the 1970s.

Brussels holds no fears for Boris. He spent part of his childhood there, made his name as a journalist there, and would not be alarmed by the prospect of negotiating to uphold British interests there. He would expect, indeed, to be a bolder negotiator than Cameron, and to make a greater success of things: and this, rather than a walk-out, is what he is promising in his Telegraph article.