The Duke of Sussex stayed for a polite drink after the ceremony came to a close at 2.45pm. But by 3.05pm he was driven out of Kensington Palace, the Daily Mail reports.
Harry had been seen arriving for the statue unveiling at 1.32pm – just 28 minutes before it was due to start.
He was reunited with Prince William for the ceremony in the Sunken Garden, one of the places Diana loved most at the palace.
Much attention was on the brothers, who have been at the centre of a rift, ahead of the event in honour of their late mother.
During a brief ceremony, with Diana’s siblings watching, William and Harry pulled away a green cloth covering the statue.
The bronze figure of the Princess is surrounded by three children and depicts her in the later years of her life.
Kensington Palace said the statue aims to reflect Diana’s “warmth, elegance and energy”, while the children represent the “universality and generational impact of the Princess’s work”.
In a joint statement, William and Harry said: “Today, on what would have been our mother’s 60th birthday, we remember her love, strength and character – qualities that made her a force for good around the world, changing countless lives for the better.
“Every day, we wish she were still with us, and our hope is that this statue will be seen forever as a symbol of her life and her legacy.
READ MORE: Harry and William Diana statue statement: What they really meant
“I was expecting to see some sort of tight lips and some jaw muscles which we saw at the Commonwealth service in Westminster Abbey before Harry and Meghan left.
“They seemed to be reasonably relaxed with one another.
“They weren’t arms around each other, it wasn’t very touchy and there wasn’t, perhaps, the usual banter of times gone by.
“But had you not known there was a serious problem between the two of them, you wouldn’t necessarily have picked it up.”
Harry and Meghan Markle, who quit royal duties last year for a new life in California, made a set of explosive claims about the Royal Family in their Oprah Winfrey interview in March.
The Duke of Sussex made further controversial comments about his family in the following weeks.
Harry’s visit to the UK is only the second time he has returned since Megxit.