'Do you want a hug?' Kate's sweet moment with overwhelmed young fan

During a surprise royal walkabout on Sunday, an adorable moment was captured between a young fan and the Princess of Wales.

Ahead of King Charles' coronation concert Prince William and Kate Middleton made an unannounced appearance in Windsor, stunning fans who'd gathered.

One encounter melted hearts, as Kate knelt down and hugged an overwhelmed child who was clearly surprised when the pair walked past.

After spotting the young girl sobbing, Kate appeared to ask if she wanted a hug.

Watch the video above.

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The child, who was wearing a headband with the Union Jack flag, nodded immediately before the pair shared an embrace.

The little girl was nervous because she was a performer at the coronation concert, with Kate reassuring her she would do an amazing job.

While the princess comforted the crying girl, William sampled a local homemade cocktail and bantered with some of the royal fans partying across streets of the UK as part of the Coronation Big Lunch.

Watch the coronation concert in full on Channel 9 and 9Now

READ MORE: Royals celebrate coronation at street parties across the UK

While the royal couple were surrounded by security, there were no fences holding the public back, allowing for a much more intimate experience.

Sue Watson, the woman who gave Prince William the homemade cocktail, told the BBC Prince William and Kate appeared with not much warning.

"All of a sudden they were here in front of us," she said.

"We thought something was happening as we saw lots of police arriving, but we didn't know who it was."

Soon before they arrived at Windsor, King Charles and Queen Camilla issued a message of thanks as thousands across the UK took part in celebratory street parties.

READ MORE: Key royal absent in William's emotional speech

Whether this is your first ever Big Lunch or whether it is an annual part of your local calendar, we send our warmest good wishes to each one of you, and all those who will be with you, at what we hope will be a truly enjoyable event for everyone," they said.

They also thanked the millions who had taken part in celebrating the coronation.