In an apparent policy shift, Britain's foreign secretary has suggested that Bashar al-Assad could be allowed to contest a future presidential election in Syria.

Since the start of the conflict in 2011, Britain has insisted that there can be no sustainable peace while Assad remains in power, though it has been willing to consider a temporary role for him in a transitional government.

On Thursday, however, foreign secretary Boris Johnson went further, saying the government is now "open-minded" about how long Assad might stay. Johnson told the House of Lords' International Relations Committee:

“We are facing the reality that things have changed and we have to think what is best for the Syrian people ...

“We are getting to the stage where some sort of democratic resolution has got to be introduced,” he added.

“I would hope it would be possible to have a plebiscite or an election which is properly supervised by the UN and in which all the 11 million displaced persons, including the four million who are outside Syria now, are fully entitled to vote.

“We believe in democracy, we support democracy, and if there is a political solution then I don’t think we can really avoid such a democratic event. I think that is the way forward.”

Johnson also recalled that during a visit to post-Saddam Iraq, his guide had told him: “It is better sometimes to have a tyrant than not to have a ruler at all.”

Allowing Assad to stay in Syria and contest an election would appear to rule out prosecution for war crimes. It also raises the question of whether his involvement would assist or impede progress towards a sustainable peace. Yemen is a prime example of how badly transitional arrangements can go wrong: the present conflict is mainly a result of allowing ex-president Saleh to stay in the country making mischief while enjoying immunity from prosecution.

Johnson has expressed a variety of opinions about Syria.

Last July, ahead of a meeting with John Kerry, then US secretary of state, he said:

“The suffering of the Syrian people will not end while Assad remains in power. The international community, including Russia, must be united on this.”

The previous March, before becoming foreign secretary, he wrote a column for the Telegraph headed: "Bravo for Assad – he is a vile tyrant but he has saved Palmyra from Isil".

An earlier column, in December 2015, had urged: "Let’s deal with the Devil: we should work with Vladimir Putin and Bashar al-Assad in Syria".

At the Foreign Office last September, Johnson hosted some Syrian opposition figures. He endorsed their blueprint for ending the conflict, describing it as "a formidably important document" and declaring that Assad could play no role in Syria's future once the six-month transition period was finished.

The Daily Mail suggests Johnson's latest remarks about letting Assad contest an election were out of line with government policy and quotes an spokesperson from the prime minister's office as saying: "Quite clearly our position is that Assad will find it impossible to form a credible government for the whole of Syria."

On the other hand, the Guardian's diplomatic editor, Patrick Wintour, detects a "dramatic reversal" of existing policy. "The defeat of the rebel opposition in Aleppo, Trump’s determination to rebuild relations with Russia, and the Turkish rapprochement with Moscow has changed the equation," he writes.