With her luminous blue eyes, blonde hair and dazzling smile, Cameron Diaz looks like a million dollars. But that does her an injustice: she’s worth an awful lot more. Last week she was named as Hollywood’s highest paid actress after earning more than £25m in a year.

The emoluments of the willowy babe have knocked Julia Roberts off the top perch and downgraded Jennifer Lopez, Sandra Bullock, the Friends star Lisa Kudrow and Meg Ryan in the pecking order.

But even Guinness World Records understates the case. Because the register’s figures are a year out of date, Diaz’s income is said to be pushing £40m thanks to the success of her new Charlie’s Angels movie.

An ingredient more elusive than physical perfection has enriched Diaz, who shot to fame as a 21-year-old unknown in The Mask and was chosen by Martin Scorsese to play a 19th-century prostitute in Gangs of New York last year.

Her secret weapon is versatility. According to a casting director: “Most actresses fit into one mould, either kooky or serious. But Cameron can do both equally well. It makes her much more marketable. Her possibilities are endless.”

The sugar and spice comes with iron filings. She can swear like a stevedore and has a weakness for greasy food and tequila. “I can be a tough bastard, yeah,” Diaz said recently. She caused a storm by belching loudly on the popular Jay Leno chat show and remarking she was glad the wind was confined to one end.

In Gangs of New York she took delight in repeatedly punching Leonardo DiCaprio’s baby face through a day of takes. By the end they were both almost unconscious. “We beat the crap out of each other,” said Diaz, who is 5ft 9in and turned 31 yesterday. “It became a test of stamina and of who could keep at it the longest without collapsing.”

Diaz’s versatility has been most recently displayed in the variable geometry of her love life. When her three-year affair with Jared Leto, her moody actor boyfriend, turned sour, she hit on an ingenious solution. Shortly before, the pouting pop stars Britney Spears and Justin Timberlake had gone their separate ways. In an act of almost poetic symmetry, they all swapped partners. Diaz is with Timberlake, seven years her junior, and Spears with Leto.

If nothing else, the gossip writers can simply rejig the storylines. We already learn that Diaz and Timberlake share a phobia about germs. While Timberlake reportedly takes four showers a day and changes his underpants six times daily, Diaz opens doors with her elbows, never leaves home without a bottle of handwash and has toilet seats sanitised before using them.

Whether this regime allows them any physical contact is difficult to assess. However, a fortnight ago the couple scored highly in a poll of coolest celebrities, along with Kylie Minogue and David and Victoria Beckham.

Not just cool: calmness has always been the Diaz trademark. Harvey Weinstein, head of the Miramax film company, has credited Diaz’s presence on the set of Gangs of New York with keeping the lid on rampant egos. “Without Cameron we would have all been screwed,” he said. “She was an angel: whenever someone’s temper flared, Cameron would be around and nobody wanted to appear to be an asshole in front of her.”

Diaz claims she has never seen the point of throwing a tantrum. “The moment you lose your temper, the views and attitudes of others towards you on the film set change.”

Nor has she often played the dumb blonde card, even changing her hair colour a few years ago to meet “more interesting men”. Brown hair was more accessible and “less intimidating”, she found.