Prince Harry has been given the title the Duke of Sussex 175 years after it was last used - and Meghan will be history's first Duchess of Sussex.
The first Duke of Sussex was an eccentric son of King George III and his two marriages were deemed illegal.
Prince Augustus Frederick was born in 1773 and died 1843 - and lived in Kensington Palace, where Harry and Meghan have their home.
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He was musically gifted, had a fine singing voice, and amassed a huge library, a variety of singing birds and a large number of clocks.
Suffering from asthma, George III's sixth son was deemed too delicate to join the military - unlike Harry, who had a 10-year stint in the armed forces.
Augustus was sent abroad and married Lady Augusta Murray - whom he called "Goosy" - in secret in Rome in 1793.
Lady Augusta Murray commonplace books are also online for the first time - which gives an intimate look at her relationship with the Duke of Sussex: https://t.co/WZAc7YI64B
-- The Royal Family (@RoyalFamily) February 16, 2018
But the marriage was declared void by George III, who had not given his approval.
It was later annulled on the grounds that it contravened the Royal Marriages Act 1772.
The prince became the Duke of Sussex in 1801.
But Lady Augusta, from whom he separated the same year, did not become the Duchess of Sussex.
She called herself princess and demanded a peerage, but never received one.
The duke's progressive political views - such as supporting the abolition of the slave trade, Catholic emancipation and political reform - sparked a rift between him and his father and brother, the Prince Regent.
The duke's second marriage was to his former mistress Lady Cecilia Buggin, who was also known as Lady Cecilia Underwood.
This was also deemed illegal because he did not seek permission from the king, so Lady Cecilia was not styled the Duchess of Sussex.
-- The Royal Family (@RoyalFamily) May 19, 2018
She was later made the Duchess of Inverness by Queen Victoria instead.
This means Meghan is history's first Duchess of Sussex.
The Duke of Sussex was Victoria's favourite uncle and he gave her away at her wedding to Prince Albert.
He was rather proud of his singing abilities, once proclaiming: "I have the most wonderful voice that was ever heard - three octaves - and I do understand music."
He was also Grand Master of the Freemasons' Premier Grand Lodge of England.
His children from his first marriage were not recognised so, when he died without a legitimate heir in 1843, this dukedom became extinct and has not been used since.
-- HistoricRoyalPalaces (@HRP_palaces) April 20, 2016
The Queen's youngest son, Prince Edward, had been expected to be given the title the Duke of Sussex when he married in 1999, but in a surprise move he received an Earldom linked to the ancient Anglo-Saxon kingdom of Wessex.
In 1874, Sussex was conferred as an Earldom with the Dukedom of Connaught and Strathearn on Queen Victoria's third son Prince Arthur William Patrick Albert.
But this earldom title became extinct on the death of his grandson, the second Duke of Connaught and Strathearn and Earl of Sussex, in 1943.
The old English county of Sussex - now made up of East and West Sussex - is located predominantly on the south coast of England, with around 90 miles of shoreline from Camber in the east to Chichester Harbour Area of Outstanding Natural Beauty in the west.
-- Visit South East Eng (@VisitSEEngland) June 20, 2017
Spanning 1,461 square miles, Sussex shares borders with Kent, Surrey and Hampshire.
Key locations include Brighton and Hove, Eastbourne, Worthing, Hastings, Crawley, the South Downs National Park, and the white cliffs at Beachy Head.
First recorded in 722 as "Suth Seaxe", the names comes from the Old English for the "territory of the South Saxons".
Although invaded by the Normans in 1066, many Sussex towns and villages still retain their original Anglo Saxon names.