A beaming Princess of Wales has made her biggest appearance since her cancer treatment ended by playing a key role in the Qatar state visit to the UK today – with Prince William offering a supporting hand to his wife.

Kate, 42, who recently finished treatment following her cancer diagnosis earlier this year, joined William to welcome Sheikh Tamim bin Hamad Al Thani and the first of his three wives, Sheikha Jawaher for the start of the huge royal event. The royals posed for traditional welcome pictures before William and Kate accompanied the guests to nearby Horse Guards Parade in Whitehall where the King and senior members of the Government were waiting and a ceremonial welcome was staged.

The princess was pictured smiling in a fitted burgundy coat by Sarah Burton for Alexander McQueen and a Sahar Millinery hat alongside William and the VIP guests inside the residence in London. Kate, wearing a pearl necklace that once belonged to the late Queen, and with her hair in a low chignon, was seen in conversation with Sheikha Jawaher.

But despite Kate being back for the ceremonial welcome, Queen Camilla was missing after suffering significantly diminished reserves of energy following her chest infection. Doctors have urged Camilla, 77, to take time to rest and recover fully because of the lingering effects of the illness, which she contracted a month ago following her long-haul trip to Australia and Samoa.

But she will join the royal party this afternoon at Buckingham Palace for a private lunch with the Emir and his wife and will also take part in all but one of the elements of the evening state banquet at Buckingham Palace, staged in honour of the Emir.

It is also hoped that the Queen will be able to view a display of Qatari artefacts after lunch in the palace’s picture gallery with her husband, the Waleses and the Emir.

More than 900 soldiers, including nearly 200 Army musicians and 100 members of the King’s Troop Royal Horse Artillery turned out at Horse Guards in honour of the guests. For this State Visit the format has been adjusted slightly to allow The King’s Troop Royal Horse Artillery to play a more visible role, and for the Emir to both see the world class troops on parade but also to hear them from within Buckingham Palace.

A Guard of Honour, formed by the 1st Battalion Welsh Guards with The King’s Colour and the Band of the Regiment waited to greet the royal guests, with William placing a supportive hand on Kate’s back. They were joined by the King’s Troop Royal Horse Artillery and a Sovereign’s Escort, under the command of Major Thomas Stewart, The Life Guards.

The King, who arrived ahead of his guests, was received at the Royal Pavilion by Sir Kenneth Olisa, His Majesty’s Lord-Lieutenant of Greater London. The Silver Stick in Waiting, Brigadier Mark Berry, and the Field Officer in Brigade Waiting, Colonel Guy Stone, were also present.

The soldiers performed a Royal Salute and a trumpeter played as the procession of the Emir passed through the grand arches of the ancient Horse Guards Building, travelling with the Prince and Princess of Wales.

As they were welcomed by the King at the Pavilion gun salutes were fired across London. The 76-year-old monarch then made a number of presentations before inviting the emir to inspect the Guard of Honour as the Qatari national anthem is played.

William was on hand to support Kate

The event is part of Kate’s gradual return to the spotlight

The royal party then departed Horse Guards in a spectacular carriage procession, accompanied by a Sovereign’s Escort of the Household Cavalry.

Charles travelled in the Irish State Coach with the Emir and Sheikha, while Kate and William followed in the Australian State Coach with His Excellency Sheikh Mohammed bin Abdulrahman bin Jassim Al Thani, the Qatari Prime Minister and Minister of Foreign Affairs.

Four other carriages carrying dignitaries formed the procession, which travelled down the Mall, past the Queen’s gardens and into the forecourt of Buckingham Palace. More pomp and pageantry awaited the Emir, as they arrived at the Palace to a second Guard of Honour and a rendition of both the British and Qatari national anthem.

State visits are considered the highest expression of friendly bilateral relations between two sovereign states, and it is a huge honour for all those taking part.

After lunch, visiting heads of state traditionally view a small exhibition of items associated with their country’s relationship with the UK and Kate will be among the royal party joining the Emir and his wife in the palace’s picture gallery for the event.

However, Kate will not attend the state banquet hosted by the King in the palace’s ballroom that evening, although William and Camilla will be there. The princess announced in September the completion of her chemotherapy treatment in a deeply personal video with her family and said her focus was “doing what I can to stay cancer free”.

The princess had been receiving treatment for an undisclosed form of cancer since late February, with the King beginning his cancer care earlier that month following his cancer diagnosis after treatment for an enlarged prostate. She has made a few official appearances, joining senior members of the Royal Family for the Remembrance Sunday service at the Cenotaph and travelling with the Prince of Wales to Merseyside to meet the bereaved families of the Southport stabbings.

William previously he was looking forward to getting back to royal duties with his wife by his side, after a ‘brutal’ year where the princess and his father the King were both diagnosed with cancer. In a wide ranging interview, William said they both wanted to evolve their roles with a focus on “helping people”.

A royal source said: “The Princess is feeling positive about the future and very much looking forward to representing the royal family at the state visit and beyond. Her work has always been a great tonic to her as she continues to concentrate on her recovery moving forward to the end of the year and beyond

Kate has a busy week and will be hosting her annual Christmas carol service at Westminster Abbey on Friday, when she is expected to be joined by her children and husband for the event. Later this afternoon, the Emir will travel to the Palace of Westminster and address gathered parliamentarians and other invited guests in the Royal Robing Room, before joining a reception with MPs and peers. William will also host the Emir at his official London home Kensington Palace.

Sheikh Tamim, 44, was educated in Britain, attending public schools Sherborne and Harrow, before graduating from Sandhurst military academy. He set up Qatar Sports Investments in 2005, which owns the French football team Paris Saint-Germain.

On Wednesday, the final day of the two-day visit, the Emir will visit Sandhurst before travelling to Buckingham Palace to bid farewell formally to the King and Queen. Sheikh Tamim will also travel to Downing Street for bilateral talks with Keir Starmer.