The king has given the happy couple his blessing and unofficial souvenirs have been on sale since the summer
If Britain was on tenterhooks over the Duchess of Cambridge's wedding dress and Monaco was agog to see Prince Albert's bride, then excitement in Spain is just high when it comes to the 85-year-old Duchess of Alba.
Unofficial souvenirs celebrating her marriage to a civil servant 24 years junior have been on the shelves since the announcement of their engagement in August.
Cayetana Fitz-James Stuart, a descendant of King James II, known for her flamboyant hippy dress and a fabulous fortune estimated at £3bn, will pledge herself to Alfonso Diez Carabantes on Wednesday.
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Last week, the groom left his job at the Ministry of Employment and was given a send off by his colleagues.
Initially, friends and family were completely opposed to the match between the twice-widowed grandee and her younger man, but gradually they have been won over by the couple's obvious devotion to each other.
Cayetana also divided up her inheritance to allay fears that her intended was after her wealth.
King Juan Carlos signalled his approval by receiving the couple in an audience at the Zarzuela Palace just outside Madrid – an honour for Alfonso, who described him as "the best".
And opera diva Montserrat Caballe congratulated the nearlyweds at a charity concert in Seville, where they plan to make their marital home in the duchess' magnificent 16th-century estate Palacio de Dueñas.
Asked why she planned to marry at her stage in life, the colourful aristocrat has a forthright answer: "I'm a practising Catholic; I'm anti-divorce, anti-abortion and all those terrible things.
"That's why I'm getting married for a third time. Unfortunately my previous two husbands died."
Indeed because of the Duchess' religious beliefs, until now the couple have never set up home together – Alfonso lived between his own home in Madrid and an annexe in Dueñas Palace.
They have, however, been acquaintances for 30 years through his brother Pedro, who was a friend of her second husband.
Their friendship deepened into love after they bumped into each other at the cinema four years ago.
Despite the doubters, he is certain that they'll be very happy together.
"I love her very much… Loving her is a privilege. People don't really know what Cayetana is like," he told HELLO!'s sister publication HOLA!
"I think I've given her happiness, dreams for the future and the desire to carry on living life to the full."