Per the Daily Mail, the couple quietly reunited Thursday at London's Heathrow Airport before taking off on their unofficial royal tour. Meghan was noticeably absent from her husband's stop in London though, where he celebrated the 10th anniversary of his charity.

Nonetheless, the Duke and Duchess of Sussex weren't apart for long ... as MM and PH reportedly linked up at Heathrow's VIP Windsor Suite before grabbing a flight to Nigeria's capital, Abuja -- where they were invited by the country's Chief of Defense Staff.

The couple kicked off their trip with a visit with General Christopher Musa ... later visiting children at the Lights Academy, where they were gifted traditional necklaces made of wooden beads.

Their schedule is jam-packed with fundraisers and receptions -- very reminiscent of what they used to do while working for the Palace. In fact, Harry is set to meet injured service members at a military hospital and Meg has been tapped to cohost a Women in Leadership event ... so they got a lot going on over there.

Now, while this visit may feel very Royal-y, it isn't on behalf of King Charles or the United Kingdom ... as the couple infamously stepped down from their royal duties in 2020.

Since then, Harry and Meghan have been estranged from the royal family ... choosing to take up residence in Santa Barbara, California. In other words, they're doing this all on their own.

There was some speculation Harry and Meghan would pick up some part-time royal duties while King Charles and sister-in-law Kate Middleton faced their respective cancer battles ... but nothing came of it. They haven't been brought back into the fold in any official capacity.