Katherine adds: “George has a very understated way of writing that’s very insightful. It’s not showy. It’s the opposite – he’s always really searching for the truth. And, you know, in a world of clickbait and sensational headlines, there’s something more old-fashioned and authentic about the way George writes. And then [director] Lewis Arnold is the other half of that partnership that I really trusted, even though I’ve never worked with him before. His track record is exceptional.

“He’s very visual, so the whole screen is speaking to you the whole time. You know, there are a lot of scenes where there’s no dialogue, and yet everything is said between characters.”

It makes for some extraordinary scenes – and emotionally intense ones, at that – but Katherine was, thankfully, able to walk away unscathed from the tragedy at the end of the shoot.

“I think it’s just the way I’m built,” she says, noting that she has played many tragic roles in her time as an actor. “I work very hard on set, you know, and I really dig and dig and dig until the final take. And then I can absolutely let it go. Because I think, ‘Well, I couldn’t have done any more than that.’

“I guess I kind of carry it around with me more beforehand in the research,” she adds, noting that she read several books in preparation for the role: Emily Jackson’s oldest living son, Neil, has worked alongside criminologist Jane Carter Woodrow on a book called After Evil, which helped Katherine fill in in all the gaps about the family. And the cast were all handed copies of Michael Bilton’s Wicked Beyond Belief [an account of the hunt for Peter Sutcliffe, which became the biggest criminal manhunt in British history].

“That’s where the work is to me,” she says. “So, afterwards, I can walk away from it. I know not everybody can, but that’s my default mechanism, I guess. And, when you meet Neil, you realise he actually did live and breathe it and he’s still living and breathing the pain of that. It gives you a lot of gratitude for your own blessings. I don’t know how you would ever get over that. And my admiration for him and the other victims is unsurpassed.”

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