The royal met the 15-year-old, known as Mutsu, in Lesotho during his 2004 gap year when the lad was just four and they kept in touch.
Touchingly, Harry gave Mutsu a pair of bright blue wellington boots during their first meeting that the youngster would not be parted from – even wearing them to bed.
Harry, 32, was so moved by his experiences he set up the Sentebale charity 10 years ago to boost the Lesotho’s impoverished children.
And in an hour-long documentary charting his project, he is shown having an emotional reunion with Mutsu in November last year at his organisation’s new Mamohato Children’s Centre in Maseru.
Harry says: “I had no mechanism to be able to start a charity than just literally being the ginger, white prince who’s come to make these children laugh. That’s what it was.”
And the pals met again earlier this year when Mutsu took his first overseas trip to London with 11 friends.
Now 16, he travelled with a choir, aided by Harry’s charity, to perform in a fundraising concert headlined by Coldplay at Kensington Palace.