David Tennant explains how he transformed into Litvinenko for drama

That served as a starting point when it came to transforming Tennant into the former Russian security officer, with the actor telling press that it was hugely important for the production to get the details of the recreation exactly right.

"That was quite a technical process, in a way, because it was about lots of people," he began. "The art department, the make-up department, the costume department, the lighting department, all trying to get their side of this image correct and me trying to, quite technically, recreate that in the first instance.

"That involved a lot of very skilled people," Tennant continued. "The make up and the prosthetics and the costume team staring at photographs to figure out, ‘What is that hospital gown and where is it arranged?’ If you can get that image right, you allow the audience into the detail of the story, I hope."

The actor went on to say that the entire transformation took "several hours" and had "a number of stages", but he feels that their efforts resulted in a resounding success.

“When we got that image and I saw it on a laptop screen, for a second you couldn’t quite tell if you were looking at the original or what we had just done," he explained.

"That was the moment you thought, ‘This feels like an effort worth making. If we can get this right and remind people of that image from 2006, then that will, hopefully, give us a great starting point to make this story as impactful as it needs to be.’"

On the original image, Tennant spoke about how strongly it still resonates in people's minds almost two decades since the horrifying incident unfolded.

"The veracity of that is very important. That image of him. When people hear his name, that’s the image that comes into most of our minds. Of that wasting body in a hospital bed. We had to get that right.

"Whether other characters look like their real life versions doesn’t really influence the telling of the story. But that image of Alexander Litvinenko that bounced around the world, that attracted the world’s attention, is so vivid and is iconic – if that is an appropriate term to use for something that is about a real human tragedy.”

Litvinenko arrives on ITVX as a full boxset on Thursday 15th December. Check out more of our Drama coverage or visit our TV Guide and Streaming Guide to find out what's on tonight.

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