Claridge's, the London hotel they call an annex of Buckingham Palace: where the Queen Mother said "yes" and where the heir to the Yugoslav throne was born in 1945

A diplomat calls a hotel in London and asks to be put through to the king. The operator asks: which one? The anecdote is told about Claridge's in London's Mayfair, the hotel they call "the annex of Buckingham Palace". The nickname isn't an exaggeration.

Its reputation began in the 19th century, when monarchs toppled from their thrones by Europe's revolutions found refuge right here. The first version of the hotel opened in 1812, and historian Martin Williams, with the help of archivist Kate Hudson, wrote its history, combing through libraries, letters and books. He was surprised that nobody had done it before him.

The Balkans have their own chapter in that story. In 1945, in one of Claridge's suites, Alexander Karađorđević was born - the son of the last Yugoslav king, Peter II. According to legend, the British government declared the suite Yugoslav territory for that day, so that the heir would be born on his own soil. The kingdom later disappeared; the hotel stayed.

In November 1947, when Princess Elizabeth married Lieutenant Philip Mountbatten at Westminster Abbey in front of around 2,000 guests, among them a crowd of kings, queens, princes and princesses, Claridge's was the centre of royal social life that week. Later, already queen, Elizabeth II met the Duchess of Windsor here for the first time in almost 30 years - discreetly, through a side door, while the Duke was recovering from treatment. Williams says the relationship with her uncle and aunt never became particularly close, but the gesture showed that there was some reconciliation after all.

The Queen Mother was, according to Williams, the hotel's most loyal friend. It was here, after dinner and dancing, on the third attempt, that she accepted the Duke of York's marriage proposal. When in 1998, for the lunch marking her hundredth birthday, the chef at her Clarence House residence couldn't manage to recreate the crab and lobster salad, Claridge's sent her the recipe.

The hotel also has a place in the story of the 20th century's most famous wedding dress. Designers David and Elizabeth Emanuel made Lady Diana Spencer's wedding dress right next to the hotel. After Diana left for her honeymoon, the Queen attended a party in the ballroom thrown by her cousin Lady Elizabeth Shakerley. On the guest list: almost the entire royal family, "six kings, eight queens", countless princes and princesses, dozens of aristocrats, several ambassadors and a maharaja.

Hollywood didn't lag behind. Audrey Hepburn's meeting with director William Wyler, key to "Roman Holiday", took place at Claridge's. Marlene Dietrich's affair with Douglas Fairbanks Jr. was noticed precisely during her stay. "She behaved rather badly," Hudson says - and adds that's exactly what she loves about her.

Kate Moss held part of her 30th birthday celebrations here in 2004, themed on F. Scott Fitzgerald's novel "The Beautiful and Damned", in the hotel's Art Deco surroundings, with cocktails and Cristal champagne. She changed into a dress that Britt Ekland reportedly wore to the premiere of "The Man with the Golden Gun" in 1974. After a party at artist Sam Taylor-Wood's, she came back to the hotel with Naomi Campbell, Tracey Emin, Grace Jones and Gwyneth Paltrow and, rumour has it, sang Gershwin's "Summertime" while Jools Holland played the piano. The staff who were there still work at the hotel - and keep quiet.

The strongest image, though, is from 1940. American playwright Clare Boothe Luce was lunching in the restaurant on the day the Dunkirk evacuation ended. Williams describes officers arriving straight from the beaches, covered in salt, sand and sweat, while elegant ladies lunched beside them. The war and the salon in one room, a few metres apart.

A hotel that welcomed deposed monarchs and where heirs were born in exile tells the simple truth about power: a title can be lost, but the address stays.