The Duke of Sussex is said to have been pictured in Canada after he and Meghan agreed a deal with the Queen to step back as senior royals.
Harry had earlier attended the UK-Africa Investment Summit in Docklands on Monday, where met the prime minister in private for 20 minutes on the sidelines.
No aides were present during the informal “catch-up” chat in a room upstairs at the summit.
Meghan returned to Canada earlier in January after the Sussexes issued a bombshell statement saying they were stepping back as senior royals.
Prince Harry: ‘There was no other option’
He told those gathered at a dinner on Sunday night: “It brings me great sadness that it has come to this. The decision that I have made for my wife and I to step back is not one I made lightly.
“It was so many months of talks after so many years of challenges.
“And I know I haven’t always gotten it right, but as far as this goes, there really was no other option.
“What I want to make clear is we’re not walking away, and we certainly aren’t walking away from you.
“Our hope was to continue serving the Queen, the commonwealth, and my military associations, but without public funding. Unfortunately, that wasn’t possible.
“I’ve accepted this, knowing that it doesn’t change who I am or how committed I am.”
Harry added that he hopes “that helps you understand what it had come to, that I would step my family back from all I have ever known, to take a step forward into what I hope can be a more peaceful life”.
He continued: “I was born into this life, and it is a great honour to serve my country and the Queen.”
The Queen held crisis talks with Prince Harry, Prince William and Prince Charles on after Harry and Meghan statement on 8 January.
A deal was later agreed where the Duke and Duchess of Sussex will lose royal funds and no longer use their HRH titles from spring.
They will also repay £2.4m of taxpayers’ money spent on renovating their Frogmore Cottage home.
They will still use the property as their base when in the UK, but it is believed they will spend the majority of their time in North America.
