Sewell dons extensive prosthetics to disappear into the role of Prince Andrew, but viewers shouldn't fear a broad or cartoonish performance according to Martin (whose other credits include The Crown and Sky's Catherine the Great).
"Casting is everything and trying to get the cast right can make or break your film, obviously," he told RadioTimes.com in an exclusive interview.
"And I think one of the challenges, one of the reasons why Gillian and Rufus are so good at what they do, is that not only do they get close to Andrew and to Emily, but they also do so in a way that humanises them."
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Martin continued: "And that helps you understand those characters' thought processes. I think that's what drama can do. I think that's what good casting can do.
"This subject has been covered really brilliantly in documentaries. But I think what drama does, what casting does, is put you into the emotional headspace of these characters. That's what's new and different about it, I think."
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He added: "And that's certainly what Rufus and Gillian did so brilliantly."
The interview that Scoop depicts was broadcast in November 2019 and remains available to watch in full on YouTube.
Scoop is available to stream on Netflix from Friday 5th April 2024. Sign up for Netflix from £4.99 a month. Netflix is also available on Sky Glass and Virgin Media Stream.
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