(tense sustained musical note) - We find the body in this series stuffed up a chimney.

(tense bewildering music) - Could it be a squirrel or a rat?

(heavy sediment pieces drop, scatter) (tense bewildering music continues) - When we were making series four I had resolved that it would end with Cassie dying.

Then as often happens, something just pings into your head and I suddenly realized oh, I've got an amazing story that would completely suit the "Unforgotten" world.

- It was quite clear, to me anyway, that Sunny's story needed to carry on.

The emotional trajectory was so terminated for him.

I was so keen to see what Sunny did.

- Season five for them picks up some months after the end of events in season four.

Sunny is still doing his job.

I'm not sure his heart is in it.

And he's finding it difficult to cope without his friend and partner.

And then has to deal with a new DCI that's come in.

I think it's probably fair to say that when our characters meet in this series at first it is tense.

- Tense or not good.

- Yes.

(Sinead chuckles) (tense music) So obvious question could it be Victoria?

- That's the obvious question.

- The child didn't have a Victorian chimney?

- Dick Van Dyke's little brother, you mean?

- Just a thought.

- My name's Sinead Keenan and I play DCI Jessica James in "Unforgotten".

At the very start of the series she's starting her new job and something terrible happens.

I literally start my new job in 54 minutes.

How could you do this?

- I'm really sorry.

- It makes her job, a job that was going to be difficult anyway because of, you know, she was taking over from beloved Cassie.

So it was never going to be easy and it's made all the more difficult.

Sorry, I sort of forgot you were there.

(tense music) - Thank you.

- Listen, DI Kahn, all I wanted to say was that I am aware of the boots that I'm filling and I sincerely hope to do her and all of her team justice.

(tense music continues) - Yeah, of course.

They're both arriving with some form of emotional baggage to deal with.

- Which makes them not quite lock horns, - No.

- But bump off each other.

This isn't therapy, DI Kahn.

This isn't your chance to somehow... Look, I don't know.

I am very sorry for the woman who died but the case is closed.

As of now.

(tense music continues) - Sinead, I'm sure, was very aware of the big boots that she had to fill.

We went for lunch with her in the beginning.

And one of the other executive producers asked if she was scared.

And she said, "I'm terrified."

(Andy chuckles) - I was a fan of the show which made it even more weird and daunting.

My agent rang me saying that people from "Unforgotten" had been in touch.

And my immediate response was no thank you.

Because who's gonna do that job?

Who's going to follow Nicola Walker?

Some idiot, no.

It turns out I'm the idiot.

There was a few of us in the mix and the other two obviously weren't available.

- Yes, it was down to you and Ray Winstone and- (Sinead chuckles) - It felt like she fit it but she'd also be completely and utterly unique.

I never worried about a single thing she did.

- [Andy] No, she didn't put a foot wrong.

- [Chris] She did not put a foot wrong.

- I think what's interesting actually is the, you know, our experiences of working with Sinead coming into the cast and the character's experience of Jess coming to work and I think absolutely mirror.

And it's a really interesting place to be because everyone is trying to kind of, you know, discover who each other is and what you're family's on, what your limits are, and how you get on.

And we're kind of doing that as actors and doing that as characters.

And I think it was, it was really clever of Chris Lang to setup the series in that way that, you know, Sunny may well be reflecting a lot of what the audience may have been feeling about the Cassie character and to play that out.

And so in a strange way that's been part of the journey through the scripts but also in real life as we all kind of get to know each other and discover that at least in real life we'd get on.

Not saying anything about the script.

- Did you apply for this job, DI Kahn?

(tense music continues) - No.

But it was offered to me multiple times.

In fact, they begged me.

(tense music softens) (door closes) (tense softened music continues)