The insight into the king’s mindset comes after Kate, Britain’s Princess of Wales, said on Friday she was undergoing preventative chemotherapy after cancer was found to be present, a fresh health blow to the royal family.

Phillips, the eldest of the late Queen Elizabeth’s eight grandchildren and son of Princess Anne, told Sky News Australia in an interview that the King was frustrated as his recovery was taking longer than he’d like.

“He’s frustrated that he can’t get on and do everything that he wants to be able to do,” he said, adding that while he was pragmatic and understood the need for recovery time, he was eager to get back to normality.

“He is always pushing his staff and everybody – his doctors and nurses – to be able to say ‘actually can I do this, can I do that?'”

Charles, 75, is hoping to attend a scaled down Easter service and family gathering next Sunday although his attendance will not be confirmed in advance.

Kensington Palace has said neither Kate nor her husband, heir to the throne Prince William, will be present for the Easter service.

Charles underwent a corrective procedure for an enlarged prostate in January. Buckingham Palace then revealed in February that he was to have treatment for an unspecified form of cancer, meaning he has had to postpone his public royal duties.

Britain’s Queen Camilla said her husband Charles was doing “very well”, as she greeted crowds on a visit to Northern Ireland on Thursday.

(Reporting by Sarah Young, additional reporting by Michael Holden, editing by Giles Elgood)