(gentle music) - The one thing that has stayed constant, brilliantly, is Cassie's relationship with Sunny.
That trust and love, that's a real touchstone in Cassie's life.
He knows her very, very well.
That doesn't change.
- In series one, we were being introduced to these characters and we kind of saw that they got on, there was mutual respect, there was a kind of playfulness between them.
And as the series progressed and Cassie has come under increasing pressure, we've seen the depth of the friendship.
Sunny kind of stepping in, his concern for her, him looking out for her.
- The fact that their relationship has just run along from the first scene, all the way through the stories so far, it's essential for them both.
- Come back in with us?
- And lose it again?
- It was one man.
- It was everything, Sunny.
- I think we've seen fragmentation of the Cassie character.
You know, dealing with the pressures, dealing with pressure at home.
And I think we see that in series four.
Cassie has been, you know, against her own wishes and judgment, come back into this arena which she's tried to escape, and Sunny's incredibly aware of that.
That sense of concern and care, and the depth of the friendship, I think, is the thing that's grown over the four series.
You okay?
- Yeah.
- Me and Sanjay, there's a bleed from real life into acting scenes with each other now.
- He's the still point for me in this show as he is for the character I play.
- Any and every scene I do with Nicola is just a joy.
- It's so much fun for actors when the relationship that you have with the person off camera is incredibly good.
- There you are.
Hello.
- Hello.
- Nicola's frozen.
She might not have frozen.
She's really good, you know.
She's very good at being still.
Look at that stillness.
You can't teach that kind of thing.
- From the first moment we clapped eyes on each other at the readthrough, we just both felt like we'd known each other forever and that everything was gonna be okay.
And that turned out to be absolutely true.
It's been a great gift, off camera and on.
