Kate and Princess Charlotte play beautiful piano duet

The Princess of Wales and her daughter Charlotte teamed up for a 'special' piano duet - with the stunning performance airing on Kate's star-studded carol concert on Christmas Eve, the Daily Mail reported.

The royal duet delighted fans during the opening segment of the programme - 'Together at Christmas' - which was on ITV1 and ITVX from 7.25pm.

It was shown alongside a voiceover of Kate reading the letter that was given to guests at Westminster Abbey, and footage of people arriving for the service on December 5.

Kate, 43, and 10-year-old Princess Charlotte played Holm Sound by Erland Cooper - a Scottish composer and producer from the Orkney Islands - whose work is inspired by nature and connection, themes which are of deep importance to the Princess of Wales.

Holm Sound was written and composed by Erland for his mother, Charlotte.

The special moment was recorded in the Inner Hall at Windsor Castle last week and the royals were joined on the day by Erland himself.

Royal fans gushed at the pair's 'absolutely beautiful' performance which 'brought tears to people's eyes' with others noting 'Catherine looks so proud of Princess Charlotte'.

One said: 'Catherine the Princess of Wales knocks it out of the park with everything she does and she makes it seem so effortless. A lovely message to accompany the piano duet with Charlotte, superb.'

Another added: 'Prince William must be so proud of both his beautiful girls. Lovely lovely carol concert.'

The Prince and Princess of Wales teased the duet on Wednesday morning by posting a cryptic surprise on their joint Instagram account.

The clip panned across a festively decorated room to show two hands, one with a large ring, resting on a piano.