The King was observed in hospital following side effects of his cancer treatment, Buckingham Palace has said.

The 76-year-old monarch cancelled his royal engagements on Friday after he “required a short period of observation in hospital” at the London Clinic, the Palace said on Thursday.

He cancelled an away day to Birmingham on Friday to prioritise his recovery as a precautionary measure and is now back at Clarence House.

He was said to be in good form at his London home, where he is working on state papers and making calls from his study.

In a statement, the Palace said: “Following scheduled and ongoing medical treatment for cancer this morning, the King experienced temporary side effects that required a short period of observation in hospital.”

It added: “His Majesty would like to send his apologies to all those who may be inconvenienced or disappointed as a result.”

It is understood the side effects, of which specifics have not been disclosed, were temporary and not uncommon with many medical treatments.