Still suspicious that her husband’s been unfaithful, GP Gemma must decide whether or not to confront Simon in next Wednesday’s Doctor Foster (BBC1).

Jonathan Strange & Mr Norrell’s Bertie Carvel lifts the lid on what it’s like playing a cheat…

What appealed to you about Doctor Foster?

“What’s amazing is that what you see in this drama is uncompromisingly recognisable in the real world. This isn’t a drama about wizards or criminals, it’s about real people having real experiences that I suspect most people watching will be able to relate to. Life is dramatic and exciting without having to be extraordinary.”

GP Gemma Foster (Suranne Jones) suspects her husband, Simon, has been cheating on her. Would you say he’s a bad person?

“Simon’s not a villain, he’s just morally conflicted. In life, people make a series of choices. Sometimes we make good ones, sometimes we make bad ones. Sometimes we make good choices for us that are hurtful to other people.”

Not knowing the truth, Gemma becomes suspicious about everyone in their social circle…

“That’s right. When you see all these other couples are around them, and their close friends and family, you realise that the tapestry of somebody’s life is interconnected in a very complicated way.”

Later, Gemma confides in former colleague Jack, who reveals Simon isn’t perhaps the man she thought she knew…

“People make assumptions about what a ‘normal’ relationship should be like and don’t challenge those assumptions until things break down. Gemma finds that a lot of her benchmarks for ‘normality’ are not what she thought.”

While there are question marks over Simon, is Gemma all that she seems?

“Simon might be selfish and a bit damaged, but Gemma isn’t simply the ‘victim’. She’s an incredibly strong woman who has led her life to this point and these things have happened to her and around her. It’s not the case that ‘these are the victims’ and ‘these are the villains’ – things are much more complex.”

Do we undercover elements of the past that might explain how Simon and Gemma got to this point?

“Yes! There’s a real ‘whodunit’ element to this series in that viewers will be questioning things like: ‘What went wrong for Gemma and Simon?’ and ‘Does he still love her?’ But, just as in real life, there are no straightforward answers.”

Did filming Doctor Foster make you suspicious of your own personal relationships?

“I suppose acting inevitably means you have to draw on a mixture of real life and imagination. You can’t hang your own life on a peg on the door and then go into work; it’s about bringing in your own experiences and assumptions. But, no, it’s fiction… thankfully!”