Kate met Rico and Russell Gray, 70, from Manchester, at a Christmas tea party, where she talked to them about their relationship.

Mr Gray has helped Rico build his confidence and develop a passion for football.

The princess asked the teenager whether his coach's guidance has "helped him with his own relationship with his friends".

Rico replied: "Yes, it's brought trust, because if you can trust one person, you can trust more people."

Mr Gray added: "If you can teach them self-reliance, responsibility, and increase their self-esteem… and if football and teamwork does all that, then you've done a good job.

"You should try and give something back and especially to children because that's where it starts."

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The visit was filmed as part of the princess's Royal Carols: Together at Christmas concert at Westminster Abbey.

It will be broadcast at 7.45pm on Christmas Eve on ITV1 and feature performances by Jacob Collier, Freya Ridings, James Bay, and a duet by Beverley Knight and Adam Lambert.

Supported by the Royal Foundation and her Shaping Us campaign, this year the service has been organised to say thank you to all those who support babies, young children and their families across the UK.