By Ian Youngs BBC News Online

With her performance in Proof in London's West End, Gwyneth Paltrow has stepped out of the security of Hollywood.

She has also stepped out of the security of a theatre festival in Massachusetts, where she first appeared as a kid and where all of her previous stage performances have taken place.

No wonder she shed a tear or two when her first show in London was over.

But they were tears of joy or, more likely, relief - rather than stress or disappointment.

[She] managed to win over a crowd waiting for her to slip up

After carving a successful career in film - with all its safety nets and short cuts - Paltrow decided to open herself up to several hundred people by going back to basics at Sam Mendes' Donmar Warehouse theatre.

With just one set, a Chicago porch, Paltrow was on stage for almost all of the two-hour show - but managed to win over a crowd waiting for her to slip up.

She had charisma and confidence, proving as capable on stage as she is on screen and disappointing those hoping for some obvious mistakes.

But there was also awkwardness, which could be put down to the fact that it was her first appearance on such an arena - but which stopped it becoming a great performance.

She played Catherine, a drifting 25-year-old who is trying to cope with the death of her mathematical genius father and work out whether she has taken on his emotional demons.

Arms 'dangled'

She cannot take any credit for the fact that it is a great role, and a great play - that goes to its author, David Auburn, and director, John Madden, who directed Paltrow on screen in Shakespeare In Love.

It is a clever family drama that seemed filmic in its style, using flashbacks to fill in the blanks of a twisting plot.

Although the play itself was a masterful work, this night was all about Gwyneth.

During the first half, she did look a little stranded on stage.

While her face was compelling - getting convincingly flushed on the many occasions when Catherine was agitated - her arms tended to dangle by her sides as if she did not know what to do with them.

That is the beauty of celluloid - it affords luxuries like close-ups.

But part of that awkwardness was down to her character, who was meant to be more like a mooching teenager than a 25-year-old.

Much of Paltrow's aloofness disappeared in the second half, when the natural actress in her came out.

She did not astound or confound - but she did answer the cynics and go some way towards dispelling the myth of being a spoilt Hollywood star.