The Princess of Wales made a rare public appearance with senior members of the royal family to welcome the Emir of Qatar to the UK at the start of his two-day state visit.

Kate looked relaxed as she joined husband William and the King in Whitehall for the ceremonial greeting missed by the Queen who revealed she has suffered a bout of pneumonia.

The past year has been a turbulent period for the royal family following the princess’s successful treatment for cancer and Charles’s ongoing care at the hands of specialists for an undisclosed form of cancer.

The princess has made a handful of official appearances since announcing in September she had completed her chemotherapy treatment and would be gradually returning to public duties.

The Emir and his wife were welcomed with a ceremony of pomp and pageantry on Whitehall’s Horse Guards Parade staged by a guard of honour formed by the 1st Battalion Welsh Guards inspected by the Gulf state ruler.

The King’s Troop Royal Horse Artillery made a rare appearance onto the parade ground and it is thought their appearance followed a request from the Emir who wanted to see more horses on display.

There were a number of public displays of affection by William towards his wife, who has said her focus is to stay “cancer free”.

Kate 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 diagnosis after treatment for an enlarged prostate.

She has made a number of 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.

Camilla later joined the royal party for a private lunch held for the visiting head of state Sheikh Tamim bin Hamad Al Thani and the first of his three wives, Sheikha Jawaher at Buckingham Palace.

Before they royal party dined Camilla, 77, told some guests her chest infection was a form of pneumonia and it is understood she missed the official welcoming ceremony due to post-viral fatigue.

It is understood the Queen’s condition was viral, not bacterial, and she no longer has the illness.

After lunch held in the palace’s Blue Drawing Rom, the King led the Emir and his guests into the Picture Gallery, where Christmas trees, decked out in white lights and golden baubles, were on show high above the grand doorways.

Following behind was the Queen, in a blue tartan dress, accompanying Sheikha Jawaher, who was dressed in a vivid red floor-length gown.

Kate and William were greeted by Tim Knox, director of the Royal Collection, as they prepared to view the exhibition of items from the Royal Collection Trust and the Turquoise Mountain Foundation relating to Qatar.

Kate, who arrived at the Palace after the ceremonial welcome on Horse Guards Parade wearing knee-high boots, had swapped her sturdy footwear for burgundy stilettos.

William stuck close to his wife’s side as they viewed the small displays of exhibits together.

At one point, they were seen laughing with one another, with Kate breaking out in a wide smile as they waited behind the King to look at the next set of artefacts.

The princess pointed at a gold mantel clock featuring a bronze model of a horse, which was given by Sheikh Tamim to the King as the prince of Wales in 2010.

Also among the group were the Duke and Duchess of Edinburgh, the Duke of Gloucester and the Duke of Kent.