Prince Charles has given his reaction to the news that he is to become a grandfather for the first time.

Catherine, the Duchess of Cambridge, left King Edward VII hospital in London on Thursday, after several days of treatment for acute morning sickness.

Speaking at the launch of Sir Ranulph Fiennes' Antarctic expedition, Prince Charles joked about the prank call made to the hospital by two Australian DJs and said he was "thrilled" at the news of the pregnancy.