Prince Harry and wife Meghan Markle are expecting their first baby in the first half of next year, Kensington Palace announced on Monday as the royal couple embarked on a four-nation tour.

"Their Royal Highnesses The Duke and Duchess of Sussex are very pleased to announce that The Duchess of Sussex is expecting a baby in the Spring of 2019," Kensington Palace said in a statement, as the royal couple arrived in Sydney on their first overseas tour as a royal couple.