The King Edward VII Hospital where Kate Middleton is being treated for extreme morning sickness fell for a hoax call and provided information about the Duchess of Cambridge's condition.
Two Australian radio presenters Mel Greig and Michael Christian called the hospital, pretending to be Queen Elizabeth and Prince Charles.
The presenters on the Summer 30 show on 2Day FM discussed the prank before calling the hospital. The entire phone conversation with hsopital staff was then broadcast on the show.
When the connection was made, Greig asked in a posh accent: "[May I] speak to Kate please, my granddaughter."
The pranksters were then transferred to a ward. While the call was being held, the duo talked about how easy the trick had been. Greig asked: "Are they putting us through?"
Christian replied: "If this works, it's the easiest prank call ever made."
When connected, a hospital staff member explained that the Duchess was sleeping. The presenters were told: "She's sleeping at the moment and she has had an uneventful night and sleep is good for her.
"She's been given some fluids to rehydrate her because she was quite dehydrated when she came in but she's stable at the moment.
"She hasn't had any retching with me since I've been on duty and she has been sleeping on and off."
The pair, who played a tape of barking Corgis in the background of their call, were also told they should visit after 9am after the doctor had visited and the Duchess had "freshened up".
John Lofthouse, chief executive of the hospital, said: "This was a foolish prank call that we all deplore. We take patient confidentiality extremely seriously and we are now reviewing our telephone protocols."