Hugh Grant and Sandra Bullock stoked rumours about their private lives when they appeared together at the London première of their new film, Two Weeks Notice, on Thursday.

About 2,000 fans braved freezing weather to see the pair, who have been at the centre of speculation about their relationship for nine months.

Grant delighted fans in Leicester Square

Joking with the crowd and reporters, the pair hugged and Bullock even pinched her co-star's bottom on the red carpet.

Grant has said that Bullock helped him rediscover the joy of film-making, and that he would love to work with the Speed star again.

When asked about the rumours of a romance, Bullock said: "That's probably as true a rumour as has been written."

The pair made a point of publicly flirting and poking fun at the speculation.

When Grant was asked to kiss Bullock, she grimaced before reluctantly offering her cheek.

I have never had so much fun making a film before Hugh Grant

The Notting Hill and About A Boy star said he would love to work with Bullock again. "But, alas, I don't think she feels the same," he said.

He said he had not enjoyed making a film since 1999 - until the experience with Bullock.

"I have never had so much fun making a film before," he said.

"I never have fun at work so it was a strange experience for me."

There has been speculation about their relationship since they made the film at the start of 2002, but they denied it at the time.

At the première, the pair spent time signing autographs and chatting to fans, and Grant took photographs of himself with his admirers.

Two Weeks Notice, which has taken $80m (£48m) at US box offices, stars Bullock as a lawyer hired by Grant, who plays a property billionaire.

The pair hate each other at first, but end up falling in love as they are forced to work together.