Q&A with Colin Teevan, Lead Writer of The Undeclared War Series Two

How did you approach writing the second series?

Second, third and fourth series are always interesting because audiences want two things at once: they want something familiar, but they also want something new.

That becomes part of the challenge. You can't simply repeat what you've done before, but you also can't abandon everything that made the original work.

For me, it became a kind of chess game. There were cliffhangers from the first series that needed to be resolved, but those resolutions also had to evolve into an entirely new story. The challenge was finding a way to honour what had come before while taking the characters and the audience somewhere unexpected.

What are the challenges that come with writing a series like this?

The first challenge is that, at its heart, the series is about cyber warfare and what organisations like GCHQ do. It's an immensely technical world.

Understanding enough about that environment to write convincingly is a significant undertaking because it's not an area I originally came from. You need to understand what your characters are dealing with on a daily basis if you're going to write them authentically.

Another challenge is that the story is rooted in contemporary geopolitics. We were fortunate to have a number of highly knowledgeable advisers on the series, but there are naturally things you are never going to be told.

As a writer, you have to take what you know, make informed assumptions and imagine what might be happening behind closed doors. It's a balance between accuracy and dramatic storytelling.

The third challenge is finding dramatic ways to depict a world that is often invisible. People can live highly active lives online, but visually that can amount to somebody looking at a screen.

In series two, I shifted the perspective towards Danny, Simon Pegg's character, who is Director of Operations. Through him, we see the consequences of the decisions being made and the pressures created by a very different kind of cyber threat.

Ultimately, though, drama is always about character. Audiences want to experience a world through someone else's eyes.

Series one asked what it would be like to enter this world through Saara's perspective. Series two asks what it is like to stand at the centre of that world and carry responsibility for decisions that could have enormous consequences.

Cyber conflict is unlike traditional warfare. You're often dealing with attacks whose origins are unclear, where motives are difficult to determine and where there are no established rules. People in this field often compare it to a game of strategy, with layers of deception and counter-deception.

But for me, the most important question is always the human one: what is it like to live in this world, and how do you maintain relationships while carrying that burden?

Why is it relevant to the geopolitical climate now?

I think one of the reasons the series resonates is because many of us feel a degree of anxiety about the online world and how dependent we've become upon it.

We store our information, our finances and so much of our daily lives in digital spaces. We've created systems that are incredibly powerful but that can also leave us feeling vulnerable.

That vulnerability sits at the heart of the series.

If critical systems were disrupted, whether healthcare, transport, immigration or communications, the consequences would be enormous. That's the responsibility our characters are dealing with every day.

Cyber warfare is also evolving constantly. Even during the time we were developing the series, we saw how significant a role cyber operations played in modern conflicts.

It's now an established part of warfare in the same way that air power became a defining aspect of twentieth-century conflict.

The technology itself is changing rapidly as well. One thing we heard repeatedly from advisers was the increasing role of artificial intelligence in malware and cyber attacks. We're entering a period where malicious software can learn and adapt as it operates.

That is both deeply concerning and dramatically compelling.

The challenge for us as storytellers was always finding ways to connect those large-scale threats to the real lives of our characters and show the human consequences.

Can you tell us about the new characters you have created?

There's always a danger in a returning series that the same handful of characters end up dealing with everything.

Because this story involves a mole hunt and a very different type of threat, I wanted to introduce people with different skills and perspectives.

One area that particularly interested me was security and vetting. To work at GCHQ, individuals go through extraordinarily rigorous checks. It's a fascinating process and highlights the importance of trust within an organisation built around secrecy.

That led to the creation of Charlie, one of Danny's oldest friends, who works in security.

I was also interested in the relationship between GCHQ, government and the military. There are areas where their responsibilities overlap, but there can also be tensions between different approaches.

That led to Roz, who comes from a military cyber background. She arrives with a very different perspective and raises important questions about how the UK should respond when it comes under attack.

Do you always respond? How do you respond? What are the consequences?

Roz allowed us to explore those debates through character and conflict.

Barbara was also hugely important to me in this series. I wanted to explore Danny's home life and the reality of a marriage built around secrecy.

Many people at GCHQ have partners who also work within the intelligence community, but even then there are limits on what they can discuss. I found that dynamic fascinating.

What does it mean to have a loving, open relationship while being unable to share significant parts of your working life? That's a rich area for drama.

What's it like seeing your scenes come to life?

One of the central ideas in the series is secrecy.

What struck all of us about GCHQ was the architecture. It's largely open-plan, but it's also full of glass partitions and spaces where people can see one another without necessarily knowing everything that's happening around them.

The set was designed in a way that allowed cameras to move freely through the space and create long sightlines. It captures something of the scale of the real GCHQ building, where you see vast numbers of people working across huge operational floors.

At first glance it can look like any modern office, but of course it isn't.

The production design team created a set with enormous visual potential. It allows intimate conversations in quiet corners as well as large-scale operational scenes, and it's been exciting to see those possibilities realised on screen.

What can audiences look forward to seeing in this series?

At one level, it's a mole hunt set within a highly contemporary world, and that's a compelling thriller in itself.

But ultimately, I hope audiences connect with the characters.

The performances across the cast are outstanding, and the story places many of those characters in situations where the personal and professional collide.

They are forced to make difficult decisions, often under extraordinary pressure.

I hope audiences find that tension compelling, while also engaging with the wider questions the series raises about the increasingly complex and dangerous world we live in.

How does it differ from the first series?

One of the key differences is perspective.

Series one was very much Saara's story. Through her, we discovered this hidden world and learned how it operates.

Series two shifts the focus towards Danny, who sits at the centre of decision-making. That change alone gives the story a very different feel.

The first series was largely about introducing audiences to this world and establishing its rules. series two takes that world and presents it with a completely new challenge, both internally and externally.

It also expands the scope of the story, exploring the connections between GCHQ, politics, government and other agencies.

There's a particularly exciting episode midway through the series that shifts perspective and turns the story on its head. Afterwards, audiences are left with a very different understanding of events.

One of the advantages of returning to a story is that you can deepen characters and relationships that were only hinted at previously. We had the opportunity to explore those layers in much greater depth this time around.

Can you describe The Undeclared War series two in three words?

Tense, complex and passionate.