She worked for Cameron during his time as shadow education secretary, and for Liam Fox as press secretary.[3] In 2005, Bertin became deputy press officer for Cameron.[3]
In 2003–04, she was paid £25,000 by Pfizer to work as a researcher for The Atlantic Bridge, a now-closed charity run by Fox, while he was shadow health secretary.[4] She was the sole employee of the charity, and worked with Adam Werritty, the executive director, but according to Fox, she did not work in any health role.[4][5]
By August 2013, it had been announced that she would be switched to director of external relations, with Graeme Wilson of The Sun taking up her old role.[6]