Her Downton Abbey alter ego, lady’s maid Anna Bates, is used to keeping secrets, but now Joanne Froggatt must deal with a modern dilemma. She is among the stars of a new BBC drama strand, The Secrets, also featuring Olivia Colman, Alison Steadman, Helen Baxendale and Ashley Walters.

The series of five stand-alone dramas has been written by four of Britain’s best up and coming writers, Nick Payne (who has written two of the episodes), Sarah Solemani, Elinor Cook and Ben Ockrent and directed by BAFTA winner Dominic Savage.

“It’s important to champion new talent because that’s where new, interesting ideas come from,” Joanne told the Daily Express.

In Elinor Cook’s The Lie, Joanne plays Lexie, who believes she has the perfect relationship until she discovers husband Philip (Ben Chaplin) is married to another woman, Zara (Emilia Fox).

“Lexie is confused when she first uncovers the truth. She knows Philip has lied to her about something and the first inkling she gets is a phone call from doctors mentioning his son,” says Joanne, 34. “She follows him to work when he is supposedly going away. He doesn’t go where he says he’s going and changes his car, so straight away there is something huge he’s lying to her about. It’s horrible to think the person you’re married to could lie to you.”

When she learns Zara is a relationship counsellor, Lexie books an appointment with her.

“Lexie wants to gather as much information as possible before she confronts Philip,” Joanne says. “She’s very angry and hurt but before she can start to process those emotions she needs to know everything she possibly can. I think she’s trying to figure out why before she feels strong enough to confront him. That’s what makes her feel like she has some power in the situation – that she’s going to choose when to face the truth of this with him and confront him – and in the meantime she is desperate to understand the details.

“I hope viewers take away Lexie’s strength from it in the end, the pain that relationships can cause and the sadness you can bring somebody if you don’t treat them respectfully,” Joanne adds. “Lexie is very strong and she’s not willing to settle for second best. I don’t think any of us should.”

The Secrets starts on BBC1 on Sunday, September 7, at 10.35pm. Joanne’s episode can be seen on Wednesday, September 10, at 10.35pm,