Prince Harry became a plate-spinning children's entertainer when Buckingham Palace was transformed into a funfair for the sons and daughters of the fallen.
The Duke and Duchess of Cambridge and Harry hosted hundreds of youngsters at the Queen's famous London home for Party at the Palace, a open-air festival in honour of the children of servicemen and women killed while serving their country.
The prince gave a moving and funny speech to the young guests, who were joined by family members, telling them: "We're here to celebrate you and to remind you that we as a family, we as a nation, and we up and down the country will never ever forget about the sacrifices that every single one of you have made."
On the palace's manicured garden lawns, children chased bubbles, made balloon animals, ate ice creams, played circus themed games and soaked up the unique atmosphere of the historic royal home.
At one point, Harry joined the widow and son of Fusilier Lee Rigby, who was killed by two Islamic extremists outside Woolwich Barracks in south east London in 2013. The pair were later jailed for life.
The prince, Rebecca Rigby, 34, and her son Jack, aged six, tried their hand at plate-spinning and shared a laugh as the royal struggled to keep his plate in the air to the amusement of watching parents and children.
The prince said in his speech: "You are all together, you are one community of people that have been through the same experiences and for that every single one of us here, all the organisers, the three of us the whole of our family and the whole of this nation, thank you so, so much for everything you guys have done.
"I can assure you that Buckingham Palace gardens have not seen this much fun, ever."
During the event, William, Kate and Harry joined children at face-painting and cupcake decorating stalls, while circus acts and magicians entertained around 850 children and teenagers.
Guests enjoyed performances by the pop star Jess Glynne and ventriloquist Nina Conti, who had the three royal hosts in stitches, while children also took part in break-dancing and beat-boxing workshops.
The tea party was organised by the royals as a special treat for the children and "to honour those whose mother or father have died fighting for their country", royal sources said.
William, Kate and Harry wanted to acknowledge "the fact that a number of young children have had to come to terms with the lost of someone very close to them at a young age".
The duke and prince have recently spoken of their devastation following the death of the mother, Diana, Princess of Wales in 1997 when they were young boys.
Harry admitted he had sought counselling to help him cope with his grief, while William said "the shock is the biggest thing and I still feel it 20 years later".
Mrs Rigby, whose son played at her feet with a balloon animal, said later: "We met Harry briefly while we were spinning the plates. He's a really nice guy."
Speaking about Party at the Palace, she said: "It's been a fantastic opportunity for both parents and children.
"It's great for the kids to meet other kids and to know there are others in the same boat, and it's a chance for the parents to meet each other and know you're in a safe environment and can ask advice of parents because they've been through things similar to you."
Mrs Rigby, who would have celebrated her 10th wedding anniversary this year, added: "Everybody here has got their own story, they've got their own reasons for being here, they're all in a similar situation to us, they've lost someone close to them whether through murder, RTA (road traffic accident), killed in action."
Harry also played at plate-spinning with George Hinchcliffe, aged three, who had dressed as his favourite superhero Spiderman for the party. George's father, Captain Richard Hinchcliffe, who served with the Royal Armoured Medical Corps, died in an accident as a civilian in 2015 shortly after leaving the RAMC.
His mother, Abigail Hinchcliffe, said it was "very emotional" to be at Buckingham Palace and watch her son playing with Prince Harry.
Also invited was Jamie Molyneux, 18, and his younger brothers and sister, Arron, Charlie and Bethany.
Their father, Lieutenant Commander Ian Molyneux, 36, from Wigan, was killed by Able Seaman Ryan Donovan when the nuclear submarine HMS Astute was docked in Southampton.
Lt Cdr Molyneux was awarded a posthumous George Medal, which is second only to the George Cross, for attempting to tackle drunken guard Donovan as he ran amok with an assault rifle during a civic visit by Southampton's mayor.
Mr Molyneux, from Wigan, who was 13 when his father died, said it was "comforting" to know his family had not been forgotten.
He said: "The Duke of Cambridge wrote to us soon after my dad was killed. It was very touching. He said he understood what we were going through as siblings, with his experience losing his mum.
"I had two choices to make. I was either going to go off the rails and end up in prison or accept what's happened and do the best I can."
Mr Molyneux is following in his father's footsteps. He passed out of Welbeck Defence Sixth Form College, Leicestershire, last year, with the award for best naval cadet.
The party ended with a special display by the RAF Falcons, the parachute display team, who parachuted over the roof of the palace into the gardens to delight of the children.