Princess of Wales beams as she joins sister Pippa Middleton and a host of stars at her annual Westminster Abbey carol concert – before George, Charlotte and Louis arrive tonight to watch her rendition of Last Christmas played on John Lennon’s piano

The Princess of Wales joined her sister Pippa Middleton at Westminster Abbey today ahead of her annual carol service, where she met celebrities taking part.

Kate Middleton was not accompanied by her family, who are expected to arrive later. She will be accompanied by her three children and her husband at the event.

Among the group waiting for Kate in the abbey's Lady Chapel were singers Beverley Knight and Adam Lambert, musician Jacob Collier and actor Jim Broadbent.

Kate's sister Pippa and husband James Matthews were also photographed arriving.

The Princess will unveil a very special festive gift to guests at the concert tonight: a rendition of Last Christmas, played on John Lennon's piano.

She has been loaned the iconic instrument – on which the former Beatle composed the song 'Imagine' – from the estate of the late George Michael.

The singer – who himself died tragically early, on Christmas Day 2016 – bought it in 2000 for a whopping £1.45 million.

His famous Christmas hit will be performed by British Grammy award-winning singer/songwriter Jacob Collier in what will undoubtedly be the highlight of the royal service, which is now in its third year.

Royal Carols: Together at Christmas is filmed tonight and broadcast on ITVI and ITVX on Christmas Eve.

Led by The Princess and supported by The Royal Foundation, WLiliam and Kate's charity, it aims to recognize those who have gone above and beyond to help others throughout the year.

This year's theme is Kate's 'Early Years' campaign, designed to highlight how important what happens to children between birth and five years is in shaping their development as adults.

Among the 1,500 invited guests tonight are parents, carers, teachers, midwives, health visitors and community volunteers.

They have all been nominated by Lord-Lieutenants from across the country or by charities linked to the Royal Family, as well as by people the Princess knows personally through her work in the field at her Royal Foundation for Early Childhood Centre.

Some families with young children who have had a particularly challenging year have also been invited after being nominated by charities with which the Princess has links.

The service, which combines traditional and modern elements, will see the Westminster Abbey choir perform alongside musicians including singers Freya Ridings and James Bey, with a special duet by Beverley Knight and Adam Lambert from The Christmas Song, made famous by Nat King Cole.

The lectures are provided by Prince Wiliam, actor Jim Broadbent, presenter Emma Willis and actor Michael Ward.

Host Roman Kemp introduces the special rendition of Last Christmas on Lennon's piano, discussing the role George Michael played in his own life (his mother, Shirlie Kemp, was one of his backup singers) and the story of the piano itself .

A source told the Mail that the instrument had been loaned by his estate, who were keen to support this year's service.

Lennon, who was murdered by gunman Mark Chapman in December 1980, bought the piano in 1970 and had it delivered to studios at his home in Tittenhurst Park, Berkshire.

The following year he composed and recorded Imagine on it, and was filmed playing the song on it for the first time for his wife Yoko Ono and the Plastic Ono band.

It became the best-selling single of his solo career

George Michael, who went on to compose his own music with it, including the title track of his 2004 album Patience, said he bought the piano because it “wasn't something that should be stored anywhere or protected.” people'.

Tonight's service will be attended by the princess's family, friends and other members of the royal family.

Although he will not attend due to a diary conflict, the King has donated Christmas trees from Windsor Great Park to decorate Westminster Abbey, which will be donated to the local community after the service.

The abbey will also be filled with sustainable, eco-friendly party decorations.

Outside, the Princess has had a special letterbox installed, with guests encouraged to take a card with them that will be distributed to children who may be struggling this year through charities such as Child Bereavement UK, East Anglia Children's Hospice, Evelina London and the British Red Crotch.

They will also be greeted with carols and carols by the Action for Children Young Carers Aloud Choir, made up of twelve young carers aged six and up.

A royal aide said the princess – who will not speak that evening but will feature in a pre-filmed introduction to be broadcast on Christmas Eve – hoped the service would remind people of “how precious” the early years of a woman's life child at a time when the world is celebrating the birth of a newborn baby.

“It reminds us how unique this time is and how precious those early years are, as we begin to form our very first relationships, bond with those closest to us and explore the world we live in” , they said.

'It also means hope. As we look to the future, we hope that our children will grow up in a happier, healthier, fairer, kinder and more tolerant world. A world based on love and compassion.

“This evening, Westminster Abbey will be filled with more than 1,500 inspiring people in appreciation of their selfless support as they work tirelessly to help the youngest members of our society thrive.”

Royal Carols: Together at Christmas airs on December 24 at 7.45pm on ITV1 and ITVX