Mel Greig and Michael Christian, who present the Summer 30 show on Australian radio station 2Day FM, called the hospital in the early hours of this morning.
Mel asked to “speak to Kate please, my granddaughter”, with the receptionist asking her to hold.
A nurse then came on the line and proceeded to give the hoax caller a full update on Middleton’s condition.
The nurse said: “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.”
The male presenter, who was pretending to be Prince Charles, asked about his son William to be told he had left the hospital around 9pm.
The King Edward VII Hospital has confirmed that the conversation took place and said in a statement: “This was a foolish prank call that we all deplore. We take patient confidentiality extremely seriously and we are now reviewing our telephone protocols.”