Daniel Radcliffe fell in love with girlfriend while shooting sex scenes

Grown-up Harry Potter star Daniel Radcliffe and his girlfriend Erin Darke fell in love while shooting sex scenes in 2013 movie Kill Your Darlings.

The British actor admits he and Erin weren't actually dating when they shot the film's most provocative scene in a library, but now he and his girlfriend have "a wonderful record of us flirting for the first time".

"There's no acting going on - not from my end, anyway," Radcliffe tells Playboy magazine. "There's a moment when she makes me laugh, and I'm laughing as me and not as my character. She was incredibly funny and smart. I knew I was in trouble."

The couple started dating last year (14) and Erin and her parents got a taste of what life is like when you invite a movie superstar to join the family at Christmas after Daniel accompanied his girlfriend to her native Detroit, Michigan for the holidays amid winter wedding rumors.

"We were sitting in her dad's living room, and the phone rang," the actor explains. "Her dad said, 'Um, it's the Detroit Free Press (newspaper)'. They were calling about a rumor that we had gone there to get married on the shores of Lake Michigan. What was great was they got his number because he's a subscriber!

"I felt really bad. Wonderfully, they found it funny."

The actor found himself being drawn to articles about his trip to Michigan, because the local reporters were so kind to him.

"I don't normally read articles about me," he adds, "but I read all of them because they were so nice: 'He ate at (restaurant) Bob Evans! He bought a T-shirt in downtown Flint...'

"These journalists in Michigan were so happy that I had a nice time there. Normally I deal with the British tabloids, so this was the sweetest media thing that ever happened to me."