John Madden could be Henry Higgins to Gwyneth Paltrow's (search) Eliza Doolittle.

First, Madden transformed nasal-voiced American Paltrow into a cross-dressing Elizabethan Brit pretending to be a man so she could act at a time when women were barred from the stage. The result was a best-actress Academy Award for Paltrow on "Shakespeare in Love," which also won the best-picture Oscar.

Now, director Madden has turned the effervescent Paltrow into the depressive prodigy of a brilliant but mentally unstable mathematician in "Proof," which played at the Toronto International Film Festival before its theatrical debut Friday.

Paltrow and Madden previously had reunited in 2002 for a London stage production of David Auburn's "Proof," a Pulitzer Prize and Tony winner. After Madden directed Paltrow in the stage version, they slipped naturally into a film adaptation.

"As you sort of go through life, you realize it's very rare to have a relationship as an actor with a director like I have with John," Paltrow said in an interview with The Associated Press alongside Madden.

"He's always sort of felt like family to me in some respects. I know exactly what he's trying to convey. I trust him so implicitly. Sometimes, you work with someone and you're sort of guarded because you're not sure about their instincts. But with him, I feel he's going to take me much further than I could get on my own."

"Proof" stars Paltrow as Catherine, a dutiful daughter who puts her own life on hold to tend to her father (Anthony Hopkins (search)), a math genius, in the last delusional years of his life.

After her father's death, Catherine agonizes that while she shares much of her father's aptitude for math, she also may have inherited his madness.

"Proof" co-stars Jake Gyllenhaal as a former student of Catherine's father and Hope Davis (search) as her no-nonsense sister.

The rapport was so complete on 1998's "Shakespeare in Love" that as they were filming, Paltrow and Madden already were talking about working together again.

"We sort of made a mental note. I kept telling Gwynnie it would be great for her to do something on stage," said Madden, a veteran British theatrical director before he turned to film. "And we had a sort of vague promise ..."

"That we would do it one day ...." Paltrow said, completing Madden's thought.

"A dance later in the evening, I think is basically what we were thinking," Madden continued.

After directing 2001's "Captain Corelli's Mandolin," Madden was preparing for his stage interpretation of "Proof," figuring he would do it with a British cast. It suddenly struck him that Paltrow would be his ideal leading lady.

The two had felt an immediate rapport that predated even "Shakespeare in Love," Madden said.

"She and I met long, long, long ago for an audition on another movie that I was not allowed to cast her in," Madden said.

"They said I wasn't pretty enough," Paltrow added. "That's a true story."

When they finally were able to work together, they found they were kindred spirits, Paltrow and Madden said.

"I think perhaps it's a relationship that's not marked by a great need to interfere with each other all the time," Madden said. "Because I think she approaches the work with a great kind of intelligence, a global intelligence of how something fits into a whole.

"Obviously, you build up a trust over a period of time, but it was pretty instant on 'Shakespeare.' I knew I could trust that she would know exactly where to go with it."

The daughter of actress Blythe Danner and producer-director Bruce Paltrow ("St. Elsewhere," "The White Shadow"), Paltrow said her father's death in 2002 after recurring throat cancer proved a painful personal backdrop to her role in "Proof."

"My relationship with my father was the most central relationship of my life from the time I was zero to 30," said Paltrow, whose dad was still alive when she did the play. "When we went to do the film, he had died. I think a lot of things had changed in my own life, but I think my relationship with him and Catherine's relationship with her father was similar or is similar in the way she feels sort of inextricably linked to her father.

"I would have been willing to do anything for my father. I would have moved in with my father to look after him if my mother had died. It's just that sort of commitment. That's just the way my family is."

Married to Coldplay frontman Chris Martin, Paltrow now is preoccupied with her own family, including their 16-month-old daughter.

Paltrow has a small part as singer Peggy Lee in next year's Truman Capote film "Have You Heard?" but she says she is scaling back on film roles now that she's a mother.

"The frequency will be much less than it ever was," Paltrow said. "I think I'll only do something if I'm sure that when it comes time to talk about it, that I'll be happy to be talking about it. That it's work I will feel proud of and that I'll learn something from doing."