Casualty's 30th anniversary series concludes tonight with a thrilling episode filmed in one take using a single camera. Written by the show's co-creator Paul Unwin, the drama covers one hour in the famous emergency department, as Duffy mentors two teenage girls Chloe and Diamond, who are getting a taste of hospital life.

RadioTimes.com went to the Casualty set in Cardiff to speak to Catherine Shipton, who was mid-way through rehearsals for Duffy's big moment in the spotlight:

How did you react when you were first told about the one-shot episode?
This was first mooted about six months ago and, initially, we all just laughed! I thought it was an April Fools come early. But when [series producer] Erika Hosington let it be known that I'd be doing a lot in it, it suddenly became real. Thankfully, I sneaked a look at a confidential copy of the script and realised it was brilliant. 

Tell us about the premise of the episode...
I'm thinking of it as Casualty bumps into Mike Leigh bumps into a living art installation! It's really driven by the performances like a stage play. The episode sees these two young work experience girls [played by Georgia Sandle and Hollyoaks's Cassius Nelson] come in to spend an hour finding out whether they want to pursue a career working in a hospital. And Muggins here is assigned to show them around, but pretty soon the pressures of the day take over.

Are you worried about fluffing lines?
If you fluff the odd word, it's not the end the world because they can change things in post production. And besides, that's how we speak in real life. It's fine - as long we don't swear. Changing visuals would be harder, of course.

What does it mean to you to have Duffy be at the centre of the drama?
Well, Paul Unwin, who co-created Casualty, has written the episode. And his original vision for Casualty 30 years ago was that it be about nurses. The working title was Front Line. Because the nurses are the ones that soak up all of the trauma and - in some cases - are actually better diagnosticians than the doctors. So for Paul to have written it is a lovely echo of what the show was originally about. 

How will you feel when it's all over?
I'll be knackered! It will feel weird, but exhilarating. Because hopefully we'll have achieved what we set out to do and it'll be really special. And then about three days afterwards, I'll sob. Because that's what I do when I'm tired - all the emotions come out.

And what does it mean to you to be rounding off the 30th anniversary year in this way?
It's amazing. Particularly seeing as we were effectively axed after two series and we got letters thanking us for our contribution and wishing us luck for the future! It was the public's support that brought it back. For me, it really is Reithian: it educates, illuminates and entertains. It's a class show and it's what the BBC does best.

The Casualty one-shot episode can be seen tonight at 9:05pm on BBC1