Barack Obama left No 10 after around an hour following a meeting with Prime Minister Rishi Sunak.
The former US president said “I’m tempted” when asked questions by the media as he re-emerged and got into a Range Rover car with Jane D Hartley, the US ambassador to the UK, just after 4pm.
No 10 said the visit to Downing Street was a courtesy call as Mr Obama was already in London.
The Prime Minister’s official spokesman said: “He was making an informal courtesy drop-in as part of his trip to London, where he is conducting work of the Obama Foundation.”
The two men met in the Number 10 study at 3pm on Monday.
The spokesman added: “I think President Obama’s team made contact and obviously the Prime Minister was very happy to meet with him and discuss the work of the Obama Foundation.”
