Foreign Secretary Boris Johnson carried out a screeching U-turn when he said he was “looking forward” to working with Donald Trump.

Last year, Mr Johnson branded the President-elect “unfit” to lead America and even of “playing the game of the terrorists”.

As Mayor of London, he was the most outspoken British politician when Mr Trump sparked outrage with his call for a complete ban on Muslims entering the US.

He also lashed out when the then-Republican presidential candidate claimed that there were “no-go areas” in London where police feared for their lives, because of a threat posed by Muslims.

On the Muslim ban, Mr Johnson said: “I think Donald Trump is clearly out of his mind if he thinks that’s a sensible way to proceed, to ban people going to the United States in that way, or to any country.

“What he’s doing is playing the game of the terrorists and those who seek to divide us. That’s exactly the kind of reaction they hope to produce.”

And on the claim of “no go areas”, he added: “I think he’s betraying a quite stupefying ignorance that makes him frankly unfit to hold the office of President of the United States.

“I would invite him to come and see the whole of London and take him round the city – except I wouldn’t want to expose any Londoners to any unnecessary risk of meeting Donald Trump.”

Mr Johnson also said: “The only reason I wouldn't visit some parts of New York is the real risk of meeting Donald Trump.”

A spokesman for Mr Johnson said lots of politicians had made comments about Mr Trump in the past, but the important task now was to "get on with the job".

The Foreign Secretary did tweet about the Republican’s extraordinary triumph, saying: “Congratulations to Donald Trump and much looking forward to working with his administration on global stability and prosperity.

“I believe passionately in the importance of the UK-US relationship and am confident we can take it forward together.”

In December 2015, Mr Trump said: “We have places in London and other places that are so radicalised that the police are afraid for their own lives. We have to be very smart and very vigilant.”

At the time, an online petition demanding he be barred from visiting the UK on grounds of his “hate speech” reached more than 100,000 signatures – delivering a debate in the House of Commons.