Russell Brand was reportedly "distressed" after realising how much he'd hurt Katy Perry during their break-up.

The actor filed for divorce from the American pop star at the end of last year, following a 14-month marriage.

The singer's new concert movie Katy Perry: Part of Me includes footage of her struggling to cope with the split. Russell apparently had no idea it had taken such a toll on her until he saw the film.

"At first he was extremely angry that it would include so much detail about their relationship. He even demanded to be sent a copy so he could see exactly what was to be shown," a source told British magazine Grazia. "However, after watching the film, he was really distressed and called Katy to talk about it. He said he'd never realised before seeing it just how much he'd hurt her."

In the documentary, Katy is seen hysterically crying before taking to the stage for one of her concerts. She also talks about how she gave her marriage everything but it still "failed" and admitted she had always believed she would have a fairy tale romance.

It's been speculated that the relationship fell apart as the pair couldn't find enough time for each other Katy was touring the world, while Russell was concentrating on making movies.

"He admitted that he always resented her touring so much but that he felt guilty for ruining the experience she'd dreamt of since being a little girl," the insider added.