Queen Camilla has visited King Charles in hospital the day after he underwent treatment for an enlarged prostate.
The King went into hospital on Friday morning and is said to be "doing well" after the procedure.
It is not known how long the King will stay there, but reports suggest he could remain over the weekend.
Ahead of the procedure, he visited the Princess of Wales who had abdominal surgery there last week.
Catherine's own treatment was successful, Kensington Palace said at the time, but she is not expected to resume royal duties for months.
Both are now currently staying at the London Clinic private hospital, near Regent's Park.
The plan for the King, 75, to have the "corrective procedure" was revealed by the Palace last week. He travelled on Thursday from Sandringham to London to have the operation.
An enlarged prostate is a benign problem - which is non-cancerous - and common in older men, according to the NHS, with about one in three men over the age of 50 having some symptoms.
The medical treatment is not significant enough to require any constitutional changes for the King's role as head of state. There will not be a need for "counsellors of state" who can stand in when a monarch is seriously ill.
The Palace said the reason the King made his diagnosis public was to send a message to other men to get their prostates checked, and following the disclosure, the NHS website saw a surge in searches about enlarged prostates, an interest welcomed by doctors and charities.
A Buckingham Palace spokesperson said the King was "delighted to learn that his diagnosis is having a positive impact on public health awareness", and added that he wanted to "thank all those who have sent their good wishes".
Queen Camilla accompanied him to the hospital in Marylebone, central London, on Friday.
Before leaving she told people inside the hospital that her husband was "doing well, thank you".
The Queen returned later on Friday evening for a visit that lasted around an hour and a half.