Sarah Parish reveals the reason for the rift in Mistresses…

In this week’s episode, do things intensify between Katie and Richard?
“Something completely unexpected and totally inappropriate develops between Katie and Richard. It’s not something she’s planned and it’s horrifying to her – and to the rest of her friends when they find out. It’s a big part of her storyline this series.”

How did you react when you found out Katie makes a play for Trudi’s husband?
“My reaction was – everyone’s going to hate me! Everyone loves Trudi and along comes horrible Katie and nicks her husband. It’s quite a difficult storyline to approach and make believable without Katie coming across as a horrible, predatory man-eater – I think we get away with it.”

Were you excited to come back to the series after a break?
“It was great to come back as it’s such a nice job. We all know each other really well. It’s like putting a comfortable pair of shoes back on, it’s fantastic! And it’s such an exciting story this time so there’s been a real buzz about it.”

Are you sad that it’s the final series?
“I think it feels right. This series has a definite finality to it and it rounds off quite nicely. But we always love to come back and would love to do the show again and again. If we get good ratings this time, who knows, we might do it again. Never say never! That’s the magic of television.”

How did you feel when you heard Joanna Lumley was playing your mother Vivienne?
“I couldn’t wait. I’m a massive Joanna Lumley fan so I was incredibly nervous when I heard. I thought – what am I going to do when I see her? Do you curtsey? Do you applaud? But she’s incredibly down to earth and one of the nicest people I’ve ever meet. She’s a lovely person to be around and I think she works very well playing my mother – and the two of us are quite deep voiced!”

In this episode we find out quite a lot about Katie’s upbringing. What do we learn about her?
“Her relationship with her mother is quite spiky and quite cool. As a child Katie was very much in love with her father and constantly wanted to please him and make him happy. Consequently, the mother and daughter relationship very much suffered and became fractured over the years. This season Katie’s love story is about her and her mother finding each other again. It’s very poignant.”

The relationships between Katie, Trudi, Siobhan and Jessica are very different this time round. How does that develop this series?
“This series is fantastic because it concentrates a lot on the women and their relationships with each other and the development of their friendships, which in way is a love story in itself. These women fall out of love and lose each other, and it’s about them trying to find each other again.”

Why do you think people love the show so much?
“I think it’s because you’ve four different characters to concentrate on. You never get bored with one storyline – if you want a change one of the other girls comes on. That type of television is always quite addictive, like Sex And The City or Desperate Housewives. Mistresses also has a guilty pleasure feel about it – you can escape in it.”

Mistresses can be seen on Thursday August 12 at 9pm on BBC1.