The quarter-century mark denoted a coming of age for the flame-haired prince, who is third in line of succession to the British throne and possesses both his mother's sense of adventure and her common touch.
The younger son of Diana and Prince Charles spent his birthday continuing his pilot training in the Royal Air Force, but he was hardly out of the spotlight.
British media ran a flood of pictures, showing Harry's steady progression from a toddler in short pants to an earnest soldier in combat gear. At each step — with his easy smile and approachable ways — he reminded many of Diana.
Other sympathetic images included the 12-year-old boy who walked behind his mother's coffin to Westminster Abbey and the confident 24-year-old who spoke movingly at a memorial service in 2007 about "the best mother in the world."
"When she was alive, we completely took for granted her unrivaled love of life, laughter, fun and folly. She was our guardian, friend and protector. She never once allowed her unfaltering love for us to go unspoken or undemonstrated," he said.
Harry and his brother Prince William were left equal shares in their mother's estate following her death in a car crash in Paris in 1997. With inheritance taxes deducted, the estate was valued at nearly 13 million pounds at the time, but its present value has not been disclosed.
The Sunday Times Young Rich List — published in April — guessed that Prince Harry and Prince William were each worth 28 million pounds ($46 million). It did not break out how much was related to Diana's estate.
Under Diana's will, the princes are entitled to all the income from their part of her estate when they are 25 and they gain access to the capital at age 30. William is now 27.
Patrick Jephson, who was involved with Diana's finances when he worked as her private secretary, said the princess' money was "very prudently" invested and that Harry will also have access to some of the considerable wealth generated by the Duchy of Cornwall, which is under Prince Charles' control.
"Of all the concerns that a young man in his position might have, money is not one of them, and likely never will be," Jephson said.
As a lieutenant in the British Army, Harry's annual pay is between 29,006 to 32,061 pounds per year ($48,000 to $53,000).
Harry and his brother each have a flat at Clarence House, Charles' official home in London. He is not covered under the government's grant to the queen, which pays for her and her husband Prince Phillips' expenses.
Dickie Arbiter, former royal spokesman and now a commentator, said Harry's new wealth was unlikely to change his life.
"I doubt whether he'll touch the money because he manages quite well with his Army salary. What does he need to spend it on? Very little," Arbiter said on Sky News.
London tabloids would beg to differ.
News reports have suggested that Harry and former girlfriend Chelsy Davy may be rekindling their yearslong romance. The Sun newspaper reported they were at a club in London for a pre-birthday celebration earlier this week.
Prince Henry Charles Albert David was born in 1984, fulfilling what Diana had called her duty to produce "an heir and a spare."
His life in the royal fishbowl has not been easy. He earned an unwanted reputation as a wild child — smoking marijuana, wearing Nazi gear to a costume party and nightclubbing his way through London's hot spots. Lately, though, he seems to have embraced a soldier's life, albeit with a few more material perks than most young officers.
Harry's military career, including a 10-week stint with the British Army in Afghanistan in 2007-2008, has helped make the public forget the earlier image of him as a thoughtless carouser.
After reportedly being seen drinking and smoking marijuana, his father dragged him off to a rehabilitation center. The prince also had to apologize four years ago when a newspaper got hold of a photograph of him wearing a Nazi swastika at a costume party.
There was more trouble when his art teacher at Eton College, Sarah Forsyth, testified at an employment tribunal that, on orders from a superior, she wrote nearly all the text of an art project that Harry submitted to pass an important exam in 2002. Forsyth won a claim of unfair dismissal against the college.
There was more embarrassment in January when a newspaper disclosed a video clip of Harry referring to a Pakistani cadet with a derogatory term.
Now, apparently happily settled into his army career, Harry has become more careful not to be seen stumbling out of posh nightspots in the wee hours of the morning. He is patron of six charities including Setebale, which he co-founded with Prince Seeiso of Lesotho to support orphans. He and his brother held a charity motorcycle drive in Africa last year.
Harry is third in the line of succession to the throne, behind his father and his elder brother.
There are precedents for younger brothers to become king, including Harry's great-grandfather, King George VI who stepped in when his elder brother, King Edward VIII, abdicated.
More likely, Harry will fall further back in the line of succession if William has children.
Jephson said the young prince went through some rocky patches but is now living up to his parents' high expectations.
"His record of service to the country, both in the army and in his royal duties, would surely make both his parents and his grandparents very proud," he said.