The Duke of Cambridge has returned to his wife's hospital bedside as it emerged that prank callers tricked a nurse into revealing information about her condition.

Australian radio DJs impersonating the Queen and Prince of Wales were given an update about Kate, who was admitted to London's King Edward VII Hospital on Monday with severe morning sickness.

William, dressed casually in beige cords and a blue sweater, arrived at the private hospital in central London at 12.15pm without acknowledging the world's media camped outside the building.

The Duke is likely to be angered by the intrusion into his wife's health, despite the call having a humorous rather than sinister motive.

The 2Day FM presenters were put through to a nurse who reportedly told them: "She's sleeping at the moment and she has had an uneventful night. She's been given some fluids, she's stable at the moment."

The prank call will be deeply embarrassing for the Edward VII Hospital, which is the medical institution of choice for the Royal Family.

The Queen, Duke of Edinburgh and Duchess of Cornwall have all been treated at the institution over the years.