With “Independence Day” scheduled for 31 January, how will the reality of departure alter history’s verdict on the last thirty years of British leaders?

Theresa May
Unless the subsequent trade deal concedes the levels of continuing EU compliance envisaged by Theresa May’s chief negotiator Olly Robbins, it is hard to see Mrs May’s reputation being restored.

Her Withdrawal Agreement’s “backstop” kept the UK within the EU’s customs union unless – in effect – the Republic of Ireland subsequently agreed otherwise. It was thrice rejected in the Commons and will be seen as a dead end. The paralysis it helped sustain was broken by a different approach from a new Prime Minister better able to communicate confidence in Brexit’s potential. He duly won a general election with the clear working majority that eluded May.

Gordon Brown
As Chancellor, Gordon Brown helped frustrate Tony Blair’s enthusiasm for the Euro. But Brown’s premiership was never defined by the UK’s relations with the EU. Although a convinced Remainer, Brown maintained a relatively low profile in both the 2016 referendum and the subsequent three years of argument and incivility. 31 January 2020 will not call for a reassessment of his role in the events that led to it – because he had little responsibility for them.

John Major
By contrast, Sir John Major and Tony Blair emerge as the former prime ministers whose legacies appear most challenged by Brexit’s realisation. From the Maastricht Treaty rebellion, to the ERM, to the Euro-joining prevarications, The Major Years – as Major would be the first to accept – were derailed by the European debate far more than by its other failings and embarrassments.

During the 1997 general election campaign, Major tried to rally his Party with the appeal to “don’t bind my hands” on whether to negotiate Britain’s adoption of the Euro. Claiming not to have a clear view on whether or not to abolish the country’s currency was either incredible or duplicitous. Either way, it was the triumph of tactics over strategy and it did not work.

The following 22 years clearly did nothing to diminish Major’s undisguised hatred for what he called his Eurosceptic “bastards.” Hoping to serve his cold dish of revenge, he chose six days before last months’ general election to team-up with Tony Blair to advise voting for candidates (none of whom were Conservative Party candidates) who wanted a second referendum. Major asserted that the 2016 result was a consequence of “fiction” and that therefore “it is extraordinary that a new vote is denied: extraordinary, and undemocratic.” Six days’ later, millions of voters duly let him down again.

Having failed where Boris Johnson succeeded, Thresa May has been gracious in acknowledging and commending the scale of the Conservatives’ victory. She has resisted the temptation to tell her successor what to do with it. By contrast, Sir John has yet to publicise his reaction. Whatever else he may yet achieve in public life, it is hard to envisage he has any future as a Tory seer.

Tony Blair
For Major’s fellow rebel with a cause, 31 January will represent an utter repudiation. Second to the consequences of the invasion of Iraq, the reality of Brexit is another shattering blow to the reputation of Tony Blair.

Which of his actions will historians focus on?  Will it be the extent of his endeavours – aided by Tom Baldwin and Alastair Campbell – to overturn the referendum result and his ultimate failure to do so?  Or will it be the decisions he took whilst Prime Minister?

In particular, will Blair be immortalised as the man who killed the thing he loved? His 2004 decision to grant migrants from the ten, mostly eastern European, countries an open border with the UK at a time when every other EU member state apart from Sweden and Ireland refused to do so, made controlled versus uncontrolled immigration a key issue in 2016.

David Cameron
The first draft of history has not been kind to David Cameron. Even the version of it he engagingly wrote in his For the Record memoir was not especially convincing on the strategy behind calling the Brexit referendum. Few have given him credit for making it possible. His Remain colleagues cannot forgive him for losing it. Leavers have withheld their gratitude because they maintain he only held the vote as a tactic to neuter UKIP and would never have called it if he thought there was a serious risk of losing it.

Until a month ago, Cameron also looked like going down in history as the man that got not just his country but also the Conservative party in a mess – it came fifth in the European elections behind the Greens – whilst going AWOL himself.

But the long view of history may now skip the short-term turbulence and focus on the strategic victory. If Johnson delivers a form of Brexit that keeps his Party together and does not obviously prove to be a political or economic calamity, then Cameron may come to be seen as the absentee father of a great change that ultimately reunited his party and set Britain upon a new course. Unintentionally for sure, but at least his place in history as an agent of change would be acknowledged.

No wonder then that, unlike Sir John Major, David Cameron responded to the general election result by enthusing, “big congratulations to Boris Johnson and all those Conservative candidates … Boris will have my full support.”