Gavin and Stacey star James Corden is set to appear in the new series of Doctor Who, the Sun has reported.
The British comic was spotted reading his script whilst on a commuter train in Cardiff.
When questioned by a nearby fan, James reportedly revealed his secret.
"We normally keep our guest stars under wraps but you can't hide a bloke like James," an insider from the cult series says.
"And now he's not coming to Wales for Gavin And Stacey any more, it's pretty obvious why he is here."