One of Spain's wealthiest women, the 85-year-old Duchess of Alba, faced a nude photo scandal today on the eve of her wedding to a civil servant 25 years her junior.

A 30-year-old photograph of the duchess as she sunbathed topless in Ibiza was splashed on the cover of the racy Spanish magazine Interviu, this week, reportedly prompting a legal threat.

"We are considering suing for interfering with her rights to privacy," her friend and lawyer Javier Saavedra was quoted as telling show business news site Vanitatis on Tuesday.

The twice-widowed aristocrat, renowned for her frizzy hair and colourful dress sense, will marry 60-year-old Alfonso Diez tomorrow in the chapel of her 15th-16th century Palacio de las Duenas in Seville.

Spain's media, particularly the lively gossip shows and press, are devouring every detail of the nuptials and the duchess' tussle with six children who were doubtful about the match.

The noble has said she had to work hard to overcome her offspring's objections.

She showered her five sons and one daughter in August with much of her estate -- palaces, mansions and treasures including masterpieces by artists from Goya to Velazquez, Murillo, Rembrandt and Rubens.

But she kept control over the assets, ranging from palaces to lavish estates reputedly worth between 600 million and 3.5 billion euros ($850 million and $5.0 billion), until her death.

The guests will be restricted mostly to family -- reportedly 30-60 people -- for the marriage itself.

It is a dramatic change from Maria del Rosario Cayetana Fitz-James-Stuart's first marriage in October 1947 described by the New York Times as "Spain's most elaborate social event since the end of the monarchy".

As a strict Roman Catholic, the duchess said in an interview on the eve of the wedding that she had no choice but to marry.

"I am anti divorce, anti abortion, anti all those atrocities," she said in an interview with the Spanish news agency EFE.

"I am a Catholic and I practice it. That is why I am marrying for a third time," said the duchess.

"Unfortunately my previous two husbands died."

The duchess, who has more titles than any other noble on Earth according to the Guinness, said there had been opposition to the marriage from her children and friends "until they realized the calibre of the man he was, he is".

According to the Spanish press, she has already introduced her betrothed to King Juan Carlos, who gave his blessing.

Gossip web site Divinity said she would offer a selection of Spanish and British-inspired dishes for the wedding including Gazpacho soup, rice with spicy lobster, beef Wellington and rice pudding.

According to the daily El Mundo, the betrothed invited friends to pre-wedding lunch in the Seville palace on Tuesday so as to include all those who were unable to fit into the ceremony itself.

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