It is unclear whether the 75-year-old monarch is attending for his prostate treatment, which was announced last week, or if he is visiting his daughter-in-law who is staying at the London Clinic having undergone abdominal surgery.

The Queen was in the car with him, which left Clarence House this morning.

The Princess of Wales remains in the hospital and her surgery last week, and on 18 January was visited by her husband, the Prince of Wales.

The King's public engagements will be postponed after he has his corrective procedure.

It is understood he shared details of his diagnosis to encourage other men who may be experiencing symptoms to get checked in line with public health advice.

On the same day William visited his wife, the Queen said during an engagement in Aberdeen on 18 January that the King is "fine" ahead of his treatment and was "looking forward to getting back to work".

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