The prime minister will be remembered for Brexit, but also for harming Northern Ireland’s place in the United Kingdom

Boris Johnson, whatever his fiercest critics might say, was by no means a disastrous prime minister.

He was a shambolic leader, he was an unreliable one, and he was guided by selfish ambition.

But the outgoing premier had big qualities too.

His personality was such that he won elections in London and nationally, the latter as both the Conservative Party leader and also as the most prominent advocate of the Leave campaign in the 2016 referendum on EU membership.

It is quite possible that if he had not given momentum to the Brexit campaign, the UK would have narrowly voted to stay with Brussels rather than narrowly voted to quit.

Underneath a clownish exterior, Mr Johnson was one of the most highly educated and intelligent politicians in the House of Commons.

So the legacy he leaves, after a relatively short tenure in Downing Street (just under three years) is a mixed one.

It has been suggested that Mr Johnson never recovered from his terrifying brush with coronavirus, which at one point left him fighting for his life. But even prior to that he was accused of being indifferent to the details of policy.

Above all however, Mr Johnson will be remembered as a man who presided over a turning point in British history, in which we departed from a European cross-national entity which was gradually adopting federal powers.

In Northern Ireland, he will be remembered as the man who introduced the NI Protocol, shamelessly discarding a pledge never to agree to such a border in the Irish Sea.

He will also be remembered for lying by denying what he had agreed. For anyone who cares about NI’s place in the UK, and how it had been maintained by successive British leaders amid a decades long IRA terror campaign, that casual concession of Mr Johnson’s towards an all-island is hard to forgive.

Whether this unhappy memory can one day be placed in a more agreeable historic context depends on whether the PM’s Northern Ireland Protocol Bill does indeed become law.