Queen Elizabeth II's grandson says people should not be surprised if the queen and her husband Prince Philip miss some engagements due to their advancing years.

Peter Phillips told ITV on Wednesday that his grandparents maintain a very heavy schedule but will sometimes have to cancel appointments given their ages.

The queen is 87; Philip is 91 and has heart disease. He missed an event this week due to poor health but later attended a service marking the 60th anniversary of the queen's coronation.

Phillips said the queen and Philip are more active than many retired people their age.

The queen and her husband have cut back on lengthy overseas travel but still maintain active public schedules inside Britain.

The queen suffered a prolonged stomach problem several months ago.