King Charles is joined by a stunning Queen Camilla and a rugged Prince William at Buckingham Palace’s glittering Diplomatic Corps reception

The King and Queen hosted a glittering diplomatic reception at Buckingham Palace this evening, with Camilla stepping out in the late Queen’s aquamarine and diamond tiara for the first time. 

Prince William joined the monarch and his wife for the grand white-tie affair, but the Prince of Wales was without the Princess of Wales, who is often a regular attendee at such events, at his side.

Kate, who finished her chemotherapy treatment in the summer and is gradually returning to public duties as she recovers from cancer, is focusing on hosting her annual Christmas carol concert in Westminster Abbey in just over two weeks time.

Camilla was dressed in a blue velvet evening dress by Fiona Clare, and opted for Elizabeth II’s small aquamarine and diamond tiara as she gathered with some 900 guests at the Diplomatic Corps reception. 

The delicate headwear – sometimes known as the aquamarine ribbon tiara – features five large aquamarines set in intricate ribbons of diamonds. It is the first time Camilla has worn the rarely seen jewellery. 

The piece has been favoured in the past by the Duchess of Edinburgh who as the then-Countess of Wessex wore it to the gala dinner celebrating the Hereditary Grand Duke Guillaume of Luxembourg’s wedding in 2012, and at the wedding of Princess Madeleine of Sweden in 2013. 

Camilla matched the stunning tiara with an aquamarine and diamond necklace and earrings from her own collection.

Her Majesty also sported the King’s new ‘family order’, a symbolic portrait of the monarch given to female family members. King Charles’ is painted on poly in instead of traditional ivory.

Meanwhile, Prince William sported a brace of honours with his ‘court dress’, including knee breeches.

His miniature medals were the: Order of the Bath, Golden Jubilee, Diamond Jubilee, Platinum Jubilee and Coronation. He also wore the Most Noble Order of the Garter Sash, with the ‘Lesser George’.

His ‘Chest Orders’ were: the Most Noble Order of the Garter (Garter Star), worn next to the Most Ancient and Most Noble Order of the Thistle (Thistle Star) Around his neck was the Great Master of the Most Honourable Order of the Bath.

It is the first time the Queen has been pictured since Buckingham Palace announced on Monday that her beloved rescue dog Beth had been put down. But she smiled widely as she made her way through the State Rooms.

Camilla, who is also recovering from a chest infection, may not stay for the whole event depending on how she is feeling, having recently returned to shortened engagements after her seasonal illness.

The King, who wore white tie with traditional knee breeches and buckled shoes, was seen chatting warmly to his guests. 

The Princess of Wales did not join the family group. In September, Catherine, 42, announced a slow and measured return to royal duties after the conclusion of her cancer treatment.

As such, she is instead focusing her energies on organising her annual carol concert at Westminster Abbey early next month.

The reception celebrates the presence in London of one of the largest Diplomatic Corps in the world and is one of the highlights of the royal calendar.

It saw the King and Queen welcome more than 500 members of the ‘Diplomatic Corps’ in all their finery to the State Rooms at the palace, highlighting the crucial role the monarch plays at the heart of British diplomacy.

The event is normally held on the first Tuesday in December but has been brought forward as it would have clashed with a State Visit of the Amir of Qatar this year. 

All ambassadors to the UK are still officially accredited to the Court of St James’s, the official royal court of the sovereign.

St James’s was traditionally the most senior royal palace until the reign of Queen Victoria, when she moved her seat of power to Buckingham Palace.

The Marshall of the Diplomatic Corps serves as the liaison between the sovereign and foreign diplomatic missions and is still stationed permanently at St James’s Palace, however.

The current incumbent, Alistair Harrison, has curated the guest list with invitations sent to all ambassadors and High Commissioners at the foreign missions in London, former Prime Ministers, the Archbishops of Canterbury and York, and other leading public figures. 

Spouses are also invited, meaning more than 1,500 guests are expected attend from around 130 different countries, making it the biggest reception held at the palace all year.

For men the dress code is national dress, white tie or court dress, which involves knee breeches for male members of the British royal family. For ladies it is also national dress or long even dress – as well as tiaras.

Each year, traditionally, there is a greeting line along which members of the Royal Family move down to welcome their guests, followed by a drinks reception, a buffet dinner and dancing in the Ballroom.

Guests in the line are normally organised by diplomatic precedence, namely the length of their time in office.

After the formalities, members of the Royal Family circulate among their guests chatting but normally leave before the dancing begins.

The history of the late Queen’s tiara is not entirely clear. Elizabeth II had another larger aquamarine piece – the Brazilian Aquamarine Parure Tiara – which was made to match a necklace given to her by the president of Brazil as a coronation gift in 1953.

There is some suggestion the smaller tiara was made from additional aquamarine jewellery gifted to the late Queen by the Governor of Sao Paulo.