As they celebrate Control's double success . . . opening The Director's Fortnight at the Cannes Film Festival and winning the Best European Film prize . . . it's obvious that they're a couple offscreen as well as on.

"I've always tried not to talk too much about my private life, " Alexandra says later at the Jimmy Z Club at the Cannes Casino, " but yes, we met on the set and, incredible but true, we fell in love and I'm very happy."

She's the daughter of a Romanian actor who ran the Bucharest National Theatre before fleeing to West Germany to escape the Nicolae Ceausescu regime when she was four. Although still only 26, she has appeared in over 40 movies. "Everything from being the dead body in a lake to being a man, " she says. "But I've been lucky to get some great parts as well, maybe because I never pushed too hard." She was the doctor's wife, Tania, in Dr Zhivago . . . a part played by Geraldine Chaplin in the original version . . . before winning international recognition as Adolf Hitler's secretary in Downfall, the Oscar-nominated study of the last 12 days in the Fuhrer's bunker before he and his cronies committed suicide.

"That was my turning point, " she says.

"It has opened many, many doors and new possibilities working in the English language."

By comparison Riley, a tall lanky singer from the little-known Leeds band 10,000 Things . . . who gives a mesmerising performance as the manic Curtis . . . is an acting novice. "He's much better than a lot of professionals I've met, " Alexandra says. "He has this magnetic presence and yet at the same time there's something very vulnerable about him. That's the crazy thing about talent. Experience can help a good actor and he can become better through experience, but there are some natural talents that are just stunning, and I think Sam is that."

Alexandra had never heard of Joy Division or Ian Curtis when she was offered the part. "For me it's been a whole new chapter. I don't have the best taste in music. It's pretty cheesy.

I'm learning, though, through my new relationship."

After Downfall she got a letter from Francis Ford Coppola. "I couldn't believe it. I thought it must be a mistake or a crazy person pretending to be Coppola. He'd seen Downfall and wanted to send me a script to read."

The script arrived by FedEx while she was on holiday with a friend in Minorca. "But when I called him, the number in the letter was temporarily not available. I thought, okay, it was a joke. No problem. Then suddenly I had him on the phone. I was in such a shock I put the receiver down. But he called back because he saw my number on his phone."

Youth Without Youth, which finished shooting in Romania last winter, is Coppola's first movie since 1997's Rainmaker. According to Walter Murch . . .

who also edited Apocalypse Now . . . it's very personal, shot for a mere $5 million raised through his winery in California.

"To him it meant a lot, " says Alexandra. "He's a very open person. You have the feeling you can go to him and ask him something and he will answer you. And yet, at the same time he is Coppola. I couldn't believe that I was standing there with him, shooting in Romania where I was born."

Youth Without Youth has been chosen to open the new Rome Film Festival in September. "It's been a crazy year for me. So now I want to live a little. I enjoy putting plants on my balcony in Berlin and spending time with my friends. Life isn't just a movie."