King Charles visited his daughter-in-law, Kate, as he remained in hospital for a second day recovering from a prostate procedure, while the Princess of Wales endured her 12th day following a major but successful abdominal operation.

Queen Camilla arrived at the London Clinic in central London in a black Audi car about noon on Saturday local time.

Wearing a white blouse and black jumper, she left about three hours later.

Camilla’s visit was her second to the private hospital since she arrived with Charles on Friday morning ahead of the procedure.

She told people inside the London Clinic on Friday that the King was “doing well” after the procedure.

A Buckingham Palace spokesman said: “His Majesty would like to thank all those who have sent their good wishes over the past week and is delighted to learn that his diagnosis is having a positive impact on public health awareness.”

It is not known how long Charles will spend in hospital but reports suggest he could remain there over the weekend.

The King arrived back in London from Norfolk on Thursday afternoon, ready for the procedure after squeezing in a couple of behind-the-scenes official duties.

Prime Minister Rishi Sunak wished the King the “very best” for his treatment and a “speedy recovery” afterwards, a Downing Street spokeswoman said.

The monarch was diagnosed with the benign condition on January 17 while staying at Birkhall, Aberdeenshire, after going for a check-up because he was experiencing symptoms.

The King is understood to have wanted to share the news to encourage other men to get themselves checked.

Charles, who only acceded to throne 16 months ago, cancelled engagements and was urged to rest by his doctors ahead of the corrective procedure.

The Queen had previously said her husband is “fine” and looking forward to getting back to work.

News of his diagnosis came on the same day that Kensington Palace announced the princess was in hospital after undergoing abdominal surgery.

Kate is not expected to carry out official engagements until after Easter, with her husband Prince William clearing his diary of official duties for the time being.

—AAP