If being able to keep a secret makes for a good Time Lord then Jodie Whittaker has passed the first test.

Sources close to the performer, who was named last week as the Thirteenth Doctor, say that she knew “for months” about getting the role.

It is thought that she was given the job at least five months ago by Chris Chibnall, the new Doctor Who showrunner who worked with Whittaker on ITV drama Broadchurch where she played grieving mum Beth Latimer. And she had to keep the secret all that time.

She even appeared at a press launch earlier this summer for her new drama Trust Me where she plays a nurse who poses as… a doctor – and managed to keep her poker face for that.

However the sources said that Whittaker did tell one person (and one person only): her husband, American actor Christian Contreras.

Whittaker is expected to start filming for the role next year for a likely broadcast in autumn 2018, with the role of her companion still undecided according to sources.

It has been said that former Death in Paradise star Kris Marshall has been chosen to accompany her Doctor in the Tardis but BBC sources say that a decision has still not been made on the casting.

Whittaker said of her new role: “I’m beyond excited to begin this epic journey – with Chris and with every Whovian on this planet.

“It’s more than an honour to play the Doctor. It means remembering everyone I used to be, while stepping forward to embrace everything the Doctor stands for: hope. I can’t wait.”

New showrunner Chris Chibnall is understood to have been committed to casting a woman in the role ever since he landed the job last year.

His statement said: “I always knew I wanted the Thirteenth Doctor to be a woman and we’re thrilled to have secured our number one choice. Her audition for The Doctor simply blew us all away.

“Jodie is an in-demand, funny, inspiring, super-smart force of nature and will bring loads of wit, strength and warmth to the role. The Thirteenth Doctor is on her way.”