Carson Hartley, four, wasted no time in running up to the royal and throwing his arms around him in a touching moment during the reception at the Park Lane Hilton hotel.
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Prince Harry receives a big hug from little Carson Hartley
The pair then exchanged high fives as Harry spoke to brave Carson’s parents about his heart condition.
The little boy, who is fitted with a portable ventilator, has a heart defect, lung disease, spina bifida, and brittle bone disease. He has had more than 40 operations in his short life.
Little wonder that his happy demeanour, and incredible bravery, instantly won over Harry.
The prince was charmed by the brave little four-year-old
"We were worried he was going to high-five Prince Harry in the face he was so excited," Carson's mum Kirsty said.
"Harry got down on his knees and had a big smile on his face while he was chatting to Carson. He couldn't believe how active he was despite all the conditions he has.
"He said he thought he was inspirational for still being so happy, but he also said that parents must be recognised too for how hard they work, which was really nice to hear."
Prince Harry is the patron of the WellChild charity, which was celebrating its tenth annual awards to recognise the courage of children and young people living with serious illnesses, as well as the dedicated families, nurses and doctors who care for them.
Prince Harry was presented with a personalised piggy bank by Olivia Ruston
The royal was also introduced to Olivia Ruston, who presented him with a pottery piggy bank she had made in his likeness – complete with curly red hair.
"Is that meant to be me? That's brilliant," Harry told Olivia, who received an award for helping to care for her severely ill sister. "I haven't had one since I was a child so I had better start saving my pennies in it."
The prince even received some babysitting tips at the event, following the recent announcement that Prince William and the Duchess of Cambridge are expecting another child.
Ahead of becoming an uncle for a second time, Harry was handed a children's DVD by 14-year-old Martin Bennett, who won an award for his positive attitude towards living with Spinal Muscular Atrophy.
Prince Harry received a DVD to help with his babysitting duties from Martin Bennett
"I thought with two of them to babysit he might need some extra help, so I gave him a DVD he could stick on to distract one of them," Martin said. "He thought it was a great idea.
"I also told him a joke, but I think it's one for his Army mates, and not for his granny."
The awards ceremony was hosted by Vernon Kay, and attended by supportive stars including Pixie Lott, comedian Russell Howard, Gaby Roslin and Alexandra Burke.
Harry has been the patron of the charity since 2007 and is guest of honour at its annual event.
In a heartfelt speech, the Prince said, "I would like to congratulate each of the award winners – your stories are moving beyond words and remind us all of how fantastic you all are.
"You are an example to us all – we can learn a great deal from your strength of character, resolve and humour in facing down challenges every day."