The Princess of Wales's abdominal surgery was a carefully guarded secret ahead of her hospital admission, it has been reported.
Kate's procedure came as a surprise to those who work closely with the royal family and within their broader circle of family friends, according to PEOPLE magazine.
The Princess, 42, was admitted to the London Clinic on 16 January and is expected to remain in hospital for ten to 14 days.
It's unlikely that Kate will return to official duties until after Easter. Her last public appearance was on Christmas Day as the royals attended church in Sandringham.
As Prince William resumed his public engagements on 11 January, there was said to be growing concern as Kate's diary arrangements were unconfirmed, according to PEOPLE.
Kensington Palace confirmed news of Kate's hospital admission and surgery on 17 January – and 90 minutes later, Buckingham Palace announced that King Charles would undergo treatment for an enlarged prostate.
The King, 75, visited his daughter-in-law Kate at the London Clinic on Friday ahead of his own treatment at the private hospital.
A Buckingham Palace spokesman said: "The King was this morning admitted to a London hospital for scheduled treatment. 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 or the exact nature of his treatment.
Kate was last week said to be "doing well", with William spending time at her bedside.
The Prince, 41, has temporarily stepped back from royal duties to care for Kate and their three children, Prince George, ten, Princess Charlotte, eight, and Prince Louis, five.
A royal source told The Sunday Times the Waleses have switched to "100% family first, day job second".
Aides insist the Princess will be out of sight over the next few months but is likely to be working behind the scenes.
"Her passion for the early years is clear – there will be a huge continuation of that campaign and she will be keen to be out continuing that conversation with the nation as soon as possible," the source told the newspaper.
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