Q&A with Siân Brooke who plays Dr. Barbara Napier

What was it about the show that initially sparked your interest?

For me, the main attraction is always great writing and strong characters. In this instance, when I read the script, I felt this world had been explored brilliantly. It's a story set within the worlds of espionage and global relations, which was a huge draw.

Then there was Barbara herself. She's been an absolute joy to play. Seeing a character on the page is one thing, but it's the process of bringing that character to life that really intrigues me as an actor. With Barbara, I immediately thought, "Wow, that's going to be quite a ride."

Tell us a bit more about Barbara.

Barbara is the senior Chinese linguist at GCHQ. She also happens to be married to Danny Patrick, played by the wonderful Simon Pegg, and she's the mother of their two children.

She's fiercely intelligent, determined and funny. At times she's idealistic, and she's a character with many layers, which makes her incredibly rewarding to play.

Can you describe Barbara's relationship with Danny?

They've been married for a long time, and that was another major draw for me in the script. It's a very real relationship. There's genuine love between them, and I think they complement each other beautifully.

They're very different people. Barbara is adventurous and not naturally a nine-to-five person, yet we find her working in this office environment. Danny is perhaps more comfortable within those structures.

What connects them is that they're both highly intelligent in very different ways, and they genuinely appreciate one another's minds. I've really enjoyed exploring that relationship and working opposite Simon.

What's it been like working with Simon Pegg?

I've loved working with Simon. Our paths had never crossed before, but it felt easy from the very beginning.

He's not only a hugely talented actor, he's also a genuinely lovely human being. It's been a joy from start to finish.

Can you tell me about some of the themes explored in the series?

It's an ambitious show because it explores enormous themes such as global politics, international relations, espionage and patriotism.

At the same time, it dives into the domestic lives of these characters. We see how their work impacts their relationships with partners, friends and colleagues.

What I love is how the series operates on those two levels simultaneously. The themes are love, patriotism, ideals, beliefs, guilt and loyalty. It's all in the mix.

Why is it relevant to the geopolitical climate now?

I think the show feels incredibly relevant because we are living in a turbulent and unpredictable world.

Our lives are increasingly online. We rely on digital systems for banking, communication and so much more. We exist within this digital landscape.

The series explores the consequences when those systems are infiltrated and compromised. It's fascinating to see both the potential impact and the vulnerabilities that come with modern life.

Can you tell us about the Hong Kong scenes shot in Cardiff?

When they told me Wales was going to double for Hong Kong, I joked that I could definitely see the similarities.

In all seriousness, it was incredible. We have the most extraordinary art department, and their attention to detail is remarkable.

For one sequence, they transformed a Mexican restaurant into a Chinese tea shop. Outside, they created an entire alleyway filled with food stalls, steam and bustling activity. It was astonishing.

I spent half my time filming little videos because I couldn't believe what they had achieved.

The only downside was that we didn't get Hong Kong's climate. We got Cardiff in December. Everyone was dressed in T-shirts and summer clothes while trying not to freeze.

How has it been working with Paul McGuigan?

Paul is a genius. I've long been a fan of his work. Film Stars Don't Die in Liverpool is an absolutely exquisite film.

When I heard he would be directing the series, I was thrilled.

I also feel a connection to him because he played such an important role in creating Sherlock, a show I joined later on. Although our paths didn't cross there, I feel I owe him a great deal.

Working with him has been an absolute joy. He brings such intelligence, creativity and passion to everything he does.

Have there been any particular behind-the-scenes moments that stood out for you?

There was one memorable day when Paul decided we should film a scene in heavy rain.

We were in Cardiff, and it happened to be an exceptionally cold day. This wasn't a brief moment in light drizzle. It was a long scene in what felt like a biblical rainstorm.

The costume department put us in flesh-coloured wetsuits underneath our costumes to try and keep us warm and dry. They weren't particularly glamorous, and we looked a bit like the Michelin Man.

Despite that, I still ended up absolutely soaked and freezing by the end of the day. It's all part of the job.

What's been your most enjoyable scene to film?

One of my favourite scenes was a major two-hander with Simon's character, Danny, towards the end of the series.

Paul likes to shoot scenes from beginning to end whenever possible, rather than breaking them into smaller sections.

This particular scene ran for around 25 minutes. Seeing that on the page was daunting, but once we started filming it felt almost like performing a play.

You enter a completely different creative space when you're able to sustain a scene for that length of time. It's something you don't often get the chance to do on television, and I loved every minute of it.

What can audiences look forward to in this series?

I think the series will open people's eyes. It will have audiences on the edge of their seats and, at times, leave them genuinely shocked.

It's also educational, but never in a dry way. It explores complex issues through compelling drama and storytelling.

What type of scenes do you prefer to film?

One of the great things about playing Barbara is that the role exists across two very different worlds.

On one hand, there's the espionage element, which is thrilling and exciting. Those scenes are enormous fun because, for a moment, you can imagine you're in a James Bond film.

On the other hand, there are the domestic scenes that explore the family lives of these characters. Danny and Barbara both work at GCHQ, and we see the emotional and human side of their lives.

I enjoy both equally. The espionage provides excitement and scale, while the relationship scenes give the story heart. That's one of the strengths of the show. It reminds audiences that behind these highly skilled professionals are real people with real emotions and relationships.

How would you describe The Undeclared War Series 2 in three words?

Heart-wrenching, thrilling and surprising.