Princess Kate and Queen Camilla stun in tiaras as they host glitzy reception at Buckingham Palace

The reception celebrates one of the largest Diplomatic Corps in the world and will see the King and Queen meet representatives of several countries.

The Princess of Wales is believed to be wearing the Cambridge Lover’s Knot tiara - a diamond and pearl-encrusted headpiece made in 1914, which was often worn by Diana, Princess of Wales - while Camilla was spotted wearing the Girls of Great Britain and Ireland Tiara.

Camilla's tiara, worn by the late Queen in her accession photographs, was a wedding gift from her grandmother, Queen Mary, when Princess Elizabeth married the Duke of Edinburgh in 1947.

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Kate completed her outfit with a shining Jenny Packham dress, her family order and Her Majesty’s Greville diamond chandelier earrings.

Camilla wore a cream embroidered evening gown by Fiona Clare paired with her garter sash and star, in family order.

The Queen’s outfit was completed with The Queen Mother’s diamond brooch (a stomacher) and the late Queen’s diamond bracelet.

Tonight’s reception comes after the Princess of Wales sympathised with patients as she officially opened a children’s surgery unit, saying taking a child to hospital is “always nerve-wracking” during a tour of Evelina London’s new facility.

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The unit enables staff to provide a one-stop service for youngsters needing surgery.

Kate said she has accompanied her children to hospital for “different things”.

The new £55million children’s day surgery unit also has artwork throughout with a space-age theme and is designed to relax young patients.

Chatting to one family in a pre-op cubicle, Kate said: “It’s always nerve-wracking as a parent; I’ve taken mine into hospital for different things.

“You’re always at least worried but you’ve got a great team (here).”

Kate was told how families benefit from the one-day service at Evelina, a children’s hospital in Lambeth, central London, and part of Guy’s and St Thomas’ NHS Foundation Trust.

Youngsters can have pre-surgery checks, the operation and recovery all in the purpose-built unit, enabling Evelina to treat an extra 2,300 children a year in addition to 11,000 already receiving surgery.

The new surgery unit, which opened to patients in July, is close to the Evelina London site and Kate visited the main building and met one of Evelina’s most famous patients, Tony Hudgell, and other children who have benefited from care as they enjoyed an art session.

Tony, now aged nine, was 41 days old when he was assaulted by his birth parents, an attack which caused multiple fractures, dislocations and blunt trauma to the face, leading to organ failure, toxic shock and sepsis.

He was left untreated and in agony for 10 days, and due to the extent of his injuries both his legs had to be amputated.

Jody Simpson, 29, and her partner Anthony Smith were jailed for 10 years in 2018.

The young schoolboy launched a fundraising campaign which has passed the £1.8million mark, his adoptive parents Paula and Mark Hudgell said after their son met Kate.

Mrs Hudgell broke down in tears after Kate posed for a photo with the family and she was hugged by the royal.

She said afterwards: “I’m just emotional and overwhelmed, she just makes such an impact and she’s just so kind and has such a big heart.”

Kate is patron of Evelina London and she was joined for the visit by the hospital’s chief executive, Gubby Ayida, who paid tribute to the visiting royal.

Ayida said: “The NHS at the moment we’ve got waiting lists, backlogs and all that. The feel good factor it brings to all staff it’s just something, it’s special…it’s lifted the whole place, it’s been amazing.”