Casualty's first ever improvised episode has been teased in a new trailer.
Airing on Saturday, December 10 at 8.10pm on BBC One and iPlayer, the popular medical drama's special episode will follow the paramedics across four days – providing viewers with a poignant insight into the difficult realities that frontline healthcare workers face on a daily basis.
The improvised scenes will see Jan (Di Botcher), Teddy (Milo Clarke), Iain (Michael Stevenson) and Sah (Arin Smethurst) deal with stressful situations, as they're pushed to their breaking points.
Related: Casualty reveals 17 spoiler pictures for improvised episode
"The actors improvised all their dialogue and we shot everything like a documentary to give it a grounded, naturalistic feel," the episode's director, Steve Hughes, said.
"It was vital to make this episode feel as authentic as possible to highlight the challenges paramedics, and the NHS as a whole, face on a daily basis.
"It was scary for the actors at first, like they were walking a tightrope without a net, but it was also freeing and exciting to be able to use their own voices and, even though most of them hadn't done anything like this before, they all rose to the challenge and I'm so proud of what we achieved."
Arin Smethurst, who plays Sah, also confirmed that the episode will mark a major turning point in their working relationship with Jan.
They explained: "Post episode, Sah and Jan's relationship develops further because Jan has supported Sah when their dad was sick.
Related: 7 huge Casualty spoilers for special improvised episode
"Now that Sah has had to take charge, and knows they can take charge, they are focused on ensuring Jan is okay – which she isn't.
"Sah wants to support Jan and also make it clear that no-one begrudges anyone for having time off when they need it.
"It becomes not so tense anymore, and there is a lot more understanding between them in the aftermath."
Casualty airs on Saturdays on BBC One, and streams on BBC iPlayer.
Read more Casualty spoilers on our dedicated homepage
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