(Cover) - EN Showbiz - Russell Brand will "stay true to his word" and not discuss Katy Perry in public.

The pair are in the process of divorcing, with their marriage breakdown captured in the singer's new tour movie Katy Perry: Part of Me. She has referred to their break-up in interviews recently, something Russell is said to be unhappy about.

"This has been a bit of a publicity disaster for Russell," an insider told Heat magazine. "He made a pact with Katy that they wouldn't talk about the split, but now she's talking about him in interviews. He was just as devastated by the split as Katy, but he feels it's important to stay true to his work and never talk about her."

It has been speculated that Russell was unable to cope with Katy's stellar career. It's also been suggested his refusal to travel to see her on tour was a factor in their break-up.

Russell was recently heckled about Katy while performing a stand-up show and told the audience that he had to be "careful" abut talking about her in such an environment because he "really, really" cares about her. (C) Cover Media