About 150 relatives and friends gathered for the ceremony which was shrouded in secrecy. The guest list included many of the rich and famous from both sides of the Atlantic. Actors Will Smith and his wife Jada Pinkett Smith were there along with the comedian Jim Carrey and model Brooke Shields. One of Britain's top celebrity couples David and Victoria Beckham were invited but only Victoria managed to attend the wedding ceremony because her husband David was ordered back to Spain to play a Real Madrid football match.

The groom is a member of one of the world's most recent religions, Scientology, which was founded in 1955 by the science fiction writer L Ron Hubbard. It's a controversial religion because some people think it tries to recruit new members by using coercive methods.

The wedding was a Scientologist service and although it had many elements familiar to traditional marriage ceremonies, including rings and wedding vows, it also included certain aspects which are fundamental to Scientology, such as vowing never to go to sleep at night without talking about any differences or disagreements first.

A spokesman for the Church of Scientology said its wedding ceremonies are not legally recognised in Italy so Katie and Tom will also have to have a civil union to make their marriage legal in the eyes of the law.

Fans who waited for a glimpse of the bride, groom and their famous wedding party were disappointed. They had to wait under overcast Italian skies to catch even the most fleeting sight of the celebrities as they rushed by in limousines or under umbrellas.

But despite the rain, there's an old Italian proverb that Katie can take heart from for the rest of her married life – a wet bride is a lucky bride. That means that if it rains on your wedding day, it's a sign you'll have a happy marriage.