The title Duke of Sussex has only been used once before by Prince Augustus in the early 1800s and had been hotly tipped by royal watchers as the dukedom Harry would receive on his wedding day.

American-born Ms Markle will become Her Royal Highness the Duchess of Sussex - the first woman ever to have the title.

Details about the titles were made public just hours before the couple exchange vows at St George's Chapel, Windsor Castle, where thousands of fans have lined the streets eager for a glimpse of the newlyweds.

While a dukedom is the highest rank in the British peerage, the Queen didn't stop there and also gave the couple Scottish and Northern Irish titles, making them the Earl and Countess of Dumbarton and Baron and Baroness Kilkeel.

Titles have traditionally been handed out as a gift from the monarch to male members of the royal family.

Harry's older brother Prince William and wife Catherine Middleton received the titles the Duke and Duchess of Cambridge when they married in 2011.

The first Duke of Sussex was Prince Augustus Frederick, the sixth son of King George III.

Augustus was known as Queen Victoria's favourite uncle and gave her away at her wedding to Prince Albert of Saxe-Coburg-Gotha.

His first marriage to Lady Augusta Murray in 1793 was annulled after the couple failed to obtain the King's permission to wed.

The couple continued to live together and had two children.

Augustus left in 1801 and Lady Augusta died in 1830. He married Lady Cecilia Underwood a year later.

Throughout his life he was plagued by health problems including asthma and in 1832 started to go blind.

He died in 1843 from erysipelas, a bacterial skin infection.

Harry will be the third Earl of Dumbarton, a Scottish title that has not been used since 1749.

It is a title that has strong military connections.

Harry will also be the first Baron Kilkeel.

Kilkeel is the capital of the ancient Kingdom of Mourne, and is home to Northern Ireland's largest fishing fleet.

Australian Associated Press