It was deemed a security risk by all involved for her to venture too far into the crowds

Spokeswoman Momentum Pictures

But it was decided that it would have been too dangerous for her to go on a walkabout and chat to fans - although many stars do so at such occasions.

Instead, she appeared on a balcony to wave to the crowds - but some fans still left in tears after failing to meet their idol.

Spears had arrived almost an hour late at the event, which was the UK premi�re of her debut film, Crossroads.

It had been Spears' "main priority" to meet and greet her fans, according to a spokesperson from film company Momentum.

Safety

"It was in fact her decision to go back outside twice to wave to the crowds," she said.

"However, after assessing the situation on the ground, it was deemed a security risk by all involved for her to venture too far into the crowds."

I was not expecting this many fans out there, this is very sweet and very flattering

Britney Spears

They were worried about the security of both Spears and the fans, she added.

It was one of the biggest crowds ever seen in Leicester Square, which is used to holding such events, and Spears was surprised by the numbers that turned out to see her.

"I'm not used to this at all," she said afterwards.

But the fans were disappointed that she could not follow the example of other big names like Tom Cruise, who spent an hour chatting to admirers at the recent premi�re of his most recent film at the same location.

Spears and Mount were hand-in-hand at the event

One banner made by fans proclaimed that its owner had "come all the way from South Africa to see you", while others carried messages like: "Britney I want to be you - you're the best."

One fan, 11-year-old Gemma Willis, had queued with mother Jane since 1530 GMT to see the star.

"Gemma's crying her eyes out because she couldn't see a thing," Mrs Willis said.

"How does Britney expect people to go and see her film if she can't be bothered to say hello to her fans?"

Fran Handley, 16, of Uckfield, East Sussex, had waited for nearly six hours in the hope of getting an autograph, but said: "It wasn't worth my time."

S Club 7's Rachel Stevens was at the premi�re

"All I saw was a flash of sequin and that was it."

Singer Charlotte Church, S Club 7 member Rachel Stevens and TV presenter Dani Behr were among the other stars who turned up.

Earlier in the day, Spears gave a hint that rumours of her split from long-term boyfriend and N'Sync singer Justin Timberlake may be true.

She told reporters that she was not in "an intense relationship" - but refused to discuss her private life further.

She was seen holding hands with her Crossroads co-star and on-screen lover Anson Mount at the premi�re, having earlier admitted that she finds him "very attractive".