Britain's Prince William, left, Prince Harry and Meghan Markle attend a Service of Thanksgiving and Commemoration on ANZAC Day at Westminster Abbey in London, Wednesday, April 25, 2018. (Eddie Mulholland/Pool via AP)

Prince Harry and his wife Meghan, the Duchess of  Sussex, will attend their first royal engagement as a married couple just three days after their wedding.

The flame-haired royal and the 'Suits' star, who wed at St. George's Chapel on Saturday afternoon, will be attending the Prince of Wales' 70th Birthday Patronage Celebration on May 22, which take place in the gardens of Buckingham Palace.

Hours before  before the pair tie the knot, Kensington Palace announced the royal couple's new titles, which is conferred by Queen Elizabeth herself.

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The palace said in a statement: "The Queen has today been pleased to confer a Dukedom on Prince Henry of Wales. His titles will be Duke of Sussex, Earl of Dumbarton and Baron Kilkeel.

"Prince Harry thus becomes His Royal Highness The Duke of Sussex, and Ms Meghan Markle on marriage will become Her Royal Highness The Duchess of Sussex."