King Charles attends Easter church service in first public ...

King Charles III attended the annual Easter church service in Windsor on Sunday, his first appearance at a public royal event since his cancer diagnosis was announced in February.

Charles, 75, and Queen Camilla shook hands with people gathered outside St George's Chapel, the resting place of his late mother Queen Elizabeth II.

King Charles and Queen Camilla greet people after attending the Easter Matins Service.(Pool: Hollie Adams via Reuters)

Anne Hoyle was one of the lucky guests who shook hands with the monarch outside St George's Chapel.

"I didn’t want to talk about his illness I just wanted to lighten the mood a bit," she said.

"I asked him how many Easter eggs he'd eaten that morning ... he smiled and said none yet!"

Anne Hoyle said King Charles looked "very well and strong".(Pool: Hollie Adams via Reuters)

She travelled from her home in Wales to be here for the day, and told him to pass on her best wishes to the Princess of Wales who is also under-going cancer treatment.

"I want to reassure the people of Australia that he is looking very well and strong," Ms Hoyle said.

"We do want Catherine back as soon as possible too."

Other guests who attended the service, including Althea Kilgore, said it was reassuring to see the king in public again.

"He looks very strong, happy, healthy, they just looked wonderful today and Queen Camilla’s outfit was fabulous," she said.

Camilla was wearing a green coat dress and an emerald and diamond brooch that was the late Queen Elizabeth's.

Queen Camilla wore a green broach that belonged to Queen Elizabeth II's.

The King and Queen thanked the public for "waiting in the cold," while telling many members of the congregation - "Happy Easter."

It's understood the monarch will not attend the usual post-service lunch reception, on the advice of his doctor.

King Charles and Queen Camilla.

Many in the British press referred to this service as "Easter lite" due to the scaled back nature of the events.

Charles has postponed all previous public engagements since Buckingham Palace announced he was to undergo treatment for an unspecified form of cancer, which was found after he had a corrective procedure to an enlarged prostate in January.

Buckingham Palace has not confirmed any future public engagements for the king.

Princess Anne also attended the church service on Easter Sunday.(Pool: Hollie Adams via Reuters)

Prince William, Princess Catherine and their children George, Charlotte and Louis did not attend the church service.

This comes after the Princess of Wales announced earlier this month she was undergoing preventative chemotherapy after cancer was discovered following abdominal surgery in January.

ABC/ Reuters