Four men were arrested last night after Tom Cruise was drenched with water at the London premiere of his new film. The individuals in question were working on a new Channel 4 comedy programme and may now be charged with assaulting the A-list actor.

Cruise reacted angrily to the prank, repeatedly calling the man who soaked him a "jerk". The actor was on a walkabout talking to some of the 5,000 fans who had packed into Leicester Square for the star-studded premiere of War of the Worlds and was accompanied by his new fiance, actress Katie Holmes.

As he answered questions from journalists a bogus reporter, wearing a white and green t-shirt, stuck out a joke microphone and used it to squirt water into Cruise's face. The star struggled to maintain his composure and rounded on the man, saying, "Why would you do that ... why would you do that ... why would you do that?"

As the prankster offered a barely audible excuse, Cruise said, "Do you like thinking less of people, is that it?" After an uncomfortable silence the joker went to walk away but Cruise said, "Don't run away."

He told his assailant, "That's incredibly rude. I'm here giving you an interview and you do that ... it's incredibly rude." Cruise then said forcibly, "You're a jerk ... jerk ... you're a jerk."

The man was escorted away by security guards and taken inside the cinema where he and the three other members of his freelance camera crew were arrested. A Channel 4 spokesman said, "The incident was for a new Channel 4 entertainment show part of which involves playing comedy pranks on celebrities and on members of the public. The water squirting was not intended to cause offence and was very much in a spirit of fun. We hope Tom Cruise will be able to see the joke in the spirit with which it was intended."

The Channel 4 show is due to air later this year and currently has no confirmed title.

A police source said the incident was being treated as a serious matter. "They are being investigated in relation to an alleged assault on Mr Cruise," he said. "It was just water, but that can be very alarming when it comes from a crowd out of nowhere."

Following the altercation Cruise dried himself off with a blue towel handed to him by an aide. He then shrugged off the incident and carried on with his walkabout which ended up lasting well over two hours.

Batman Begins actress Holmes was never far from his side, but was not next to him when he was squirted. The couple, who got engaged in Paris recently after a whirlwind romance, kissed and held hands as they both signed autographs for fans. Talking about his love for the 26-year-old actress Cruise, 42, raised both his arms and punched the air. He said, "It feels great, magical. It's beautiful and it's extraordinary and I'm very happy. She's terrific, generous and really smart and really funny. I just think it's great to be in love."

Referring to his recent enthusiastic public shows of affection, including a bizarre appearance on the Oprah Winfrey Show, he said, "I try to restrain myself but I can't."

The twice married star said no date had been set for the wedding, adding, "I just proposed to her so we are going to see ... soon. We are going to sit down and think about it. There is going to be a wedding. We don't know when, we don't know where."

Asked if he would be having a riotous stag do, he laughed and said, "I'm not into bachelor parties."

For the premiere, Leicester Square was turned into a wasteland inspired by the film with upturned cars, rubble, toppled telephone boxes and camouflage netting strewn around. A series of loud explosions, fireworks and 20ft high fireballs were let off to screams from fans. Some of them had waited up to 12 hours in the sweltering heat to see Cruise and Holmes.

Cruise, who is famed for marathon walkabouts, did not disappoint them. He used some fans' mobile phones to talk to their friends as he toured the crowd dressed in jeans and a dark shirt and suit jacket.

Holmes, who wore a sparkly dark blue dress and black high heels, seemed happy for her new fiance to have most of the attention.

Cruise said the film was a "great ride" and praised director Steven Spielberg.

"I think Spielberg is unbelievable, there is great suspense and it's a very exciting story," he said.

He also heaped praise on his 11-year-old co-star Dakota Fanning, saying, "I love Dakota, she's a great actress. It doesn't matter what age she is, she's a great actress and I loved working with her."

Dakota, who treated the crowd to one of her trademark screams, said, "People will have such a blast seeing it and Tom has made it so much fun for me."

In the film, Cruise plays Ray Ferrier, a divorced dad who must save his children when aliens come to destroy the earth. Ferrier is a less-than-perfect father but Cruise said there were few similarities between him and the character. Dedicating the film to his children, he said, "I'm totally different as a parent. I always wanted to be a father and I love being a father, it's a very different role. The kids are amazing, they are my dear friends and extraordinary people."

Spielberg had wanted to make War of the Worlds since he bought the script of Orson Welles's radio play version 12 years ago. The actor's broadcast in 1938 famously proved so believable that it panicked listeners into believing the world was really under attack.

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