King Charles taken to hospital after cancer treatment side effects

Britain's King Charles spent a brief time under observation in hospital on Thursday after experiencing side effects from treatment for cancer, Buckingham Palace said, with royal sources saying it was just a "minor bump in the road".

The 76-year-old king has been undergoing treatment since he was diagnosed with an unspecified form of cancer in February last year following tests after a corrective procedure for an enlarged prostate.

The palace said he had returned to his home Clarence House, and that as a precaution his engagements for Friday would be rescheduled. His wife, Queen Camilla, had not accompanied him to hospital.

"His majesty was due to receive credentials from the ambassadors of three different nations this afternoon. Tomorrow, he was due to undertake four public engagements in Birmingham and is greatly disappointed to be missing them on this occasion," a palace spokesperson said.

"He very much hopes that they can be rescheduled in due course and offers his deepest apologies to all those who had worked so hard to make the planned visit possible."

The palace declined to give any details of the side effects. But a royal source described Thursday's setback as no more than the "most minor bump in the road that’s very much heading in the right direction" and that it was not uncommon with medical treatments.

The king's recovery was continuing in a very positive direction and that he was in good form, and was continuing to work and make calls from his study, the source said.

His state visit to Italy next month along with the queen was expected to go ahead as planned, and no other health update is anticipated.

Charles' initial cancer diagnosis came as a shock less than 18 months into his reign.

However, royal aides have been upbeat about his health since and while his diary is carefully managed, he has returned to a busy schedule of work.

Renowned as a workaholic who often worked until late on his official papers, Camilla and other family members have said he needed to be encouraged to slow down.

The royal source said the king's medical team were fully involved in discussions over his schedule, saying reactions to treatment could be unpredictable.

The king's illness has coincided with that of his daughter-in-law Kate, 43, the wife of his elder son Prince William, who also has undergone treatment for cancer.

She said in January she was now in remission and has gradually been returning to duties.