Season 1 recap | Season 2 plot | Where to watch | Why you should watch | Filming locations | Full cast | Trailer | Episode Guide | Release date
Four years after The Undeclared War first had us glued to our screens, Simon Pegg's cyber-thriller is finally back. Season 2 lands on 21st July 2026 and promises eveeeeen higher stakes, bigger political tensions and a brand-new threat for the team at GCHQ!
Alongside returning favourites Simon Pegg, Hannah Khalique-Brown and Alex Jennings, the new season brings several fresh faces to our screens including Blue Lights star Siân Brooke.
We headed to an exclusive preview screening and cast Q&A, so whether you're looking for the release date, cast, plot details or behind-the-scenes insights, here's what you need to know before season 2 begins...
The Undeclared War season 1 recap
Espionage is brought to life through a completely different lens in The Undeclared War! Rather than taking us inside MI5 or MI6 like your typical British spy thriller, Simon Pegg leads the cast in this cyber-thriller set inside GCHQ – and honestly, it’s a refreshing change.
In the first season we see placement student Saara Parvin's first day at GCHQ unfold with a flurry of chaos, a huge cyber-attack takes down internet services, with fingers being pointed at Russia, Saara is thrown into the middle of a national security crisis. Talk about a memorable first day!
As the series unfolds, we watch political tensions simmer towards breaking point, Saara's personal life begin to fall apart and we get a raw, gripping insight into an organisation that most of us know very little about. It's clever, tense and gives espionage a modern twist that feels incredibly relevant.
The other side of the story explores the power of misinformation and deep fakes through the character of Marina Veslova (played by Tinatin Dalakishvili), who leaves Russia to become a presenter for Russian Global News.
Psssst spoiler alert! If you haven't watched season 1 yet, we'd skip the next section for now. Go binge all six episodes, then come straight back!
What to expect from season 2 of The Undeclared War:
Following the aftermath of one of the biggest cyber-attacks in history, The Undeclared War season 2 picks up with GCHQ facing challenges on all fronts. Without America's support and with the Prime Minister and Defence Secretary (soon to become Foreign Secretary) breathing down their necks, the pressure is well and truly on.
After Vadim Trusov passes on exclusive intelligence from the heart of Putin's government, the team must decide what their next move should be and whether they can rebuild their relationship with America before it's too late.
As they begin investigating how the third stage of the cyber-attack was able to happen, the team uncover something even more alarming – evidence that there's a mole buried deep within GCHQ. And this isn't just anyone... it's someone in a very senior position.
And then there's Saara. After everything they've been through, her priority is simple: find Vadim and make sure he's safe before the FSB find out his involvement.
Now, we don't want to spoil toooo much (where's the fun in that?), but one thing we can tease is that The Undeclared War is heading somewhere new this season. So get ready to swap Russia for China as the story expands, the political tensions ramp up, and the stakes get even higher.
Where can I watch The Undeclared War season 2?
The Undeclared War season 2 starts on 21st July 2026 on Channel 4. You can watch it live on Channel 4 and stream episodes through Channel 4's on-demand service. Andddd if you're a Freely user, you can also add the series to My List so you're ready when new episodes arrive.
Why should you watch The Undeclared War?
This truly isn't your average espionage thriller, and that's exactly why we love it.
What really captivated us (and plenty of the audience) in the first season is the way we're transported into the world inside her head. The camera goes from her sat at her desk to in her mind where she's exploring different scenarios, solving problems and interacting with a computer that appears before her. It's such a clever way of bringing coding to life and makes you feel like you're solving the puzzle right alongside her.
It's little details like this that make The Undeclared War stand out from other spy dramas. Instead of relying on big action scenes, it finds exciting and creative ways to build tension – and it works brilliantly.
Oooo... and let's not forget Saara's iconic tech toolbelt.
Where is The Undeclared War filmed?
Season 2 of The Undeclared War was filmed primarily in Cardiff but was a mixture of purpose-built sets and real locations to bring GCHQ to life.
This season the designer got to go into the organisation itself to get inspiration from how it’s designed inside butttt of course they weren’t able to take any photos so they had to draw everything by hand. And the attention to detail clearly paid off. During the Q&A, writer Colin Teevan revealed that when the first episode was screened at GCHQ, even the organisation's Director was surprised by just how accurate the recreated sets looked. We'd call that a job well done!
Oh, and here's one more exclusive fact we have to share...
The production team were also granted two days of drone filming around iconic Doughnut headquarters – something that's incredibly rare. Keep your eyes peeled because you might just spot some angles of the famous building you've never seen before!
Who is starring in Season 2 of The Undeclared War?
Simon Peggs returns as Danny Patrick taking on a bigger role this season alongside Danny’s wife Barbara (Siân Brooke, Blue Lights) who joins as a Senior Analyst in the China Department at GCHQ. Alongside these two, the lovely Hannah Khalique-Brown is back as Saara Parvin!
Simon Pegg
Simon Pegg plays Danny Patrick the Chief of Operations at GCHQ who is the key point of contact between the intelligence professionals, hackers and David Neil, the CEO. His character is very diplomatic, and we are expecting to see a lotttt more depth to his character.
Fun fact! Simon Pegg had two uncles called Tony who both used to work at GCHQ and his brother Steve did the wiring of the new building!
Hannah Khalique-Brown
Hannah Khalique-Brown returns as Saara Parvin, a computer science student who joined the GCHQ Malware department on placement. Season one saw her character go through losing her father, understanding herself and her identity and of course, learning all the challenges that come with working in espionage. We’re expecting to see her career at GCHQ escalate in season 2 when she's pulled in to help identify a mole within the team.
Siân Brooke
Siân Brooke (Blue Lights) joins us in season 2 as Barbara, the wife of Danny Patrick and ex MI6 agent, who also works at GCHQ but as a Senior Analyst in the China Department. What we learnt at the Q&A is this is quite common because although they can’t talk to each other about what they do within separate teams and departments they at least have a mutual understanding of the pressures.
We can’t wait to see Siân’s performance in this role and the dynamic between the two characters both at home and in the workplace.
Alex Jennings
Alex Jennings (The Crown) returns in season two as David Neil, the CEO of the GSHQ who is hard working, loyal and much loved by his staff.
Jason Tobin
Known primarily for his role as Mr. Lao in A Thousand Blows Jason Tobin joins the cast for season 2.
Ed Stoppard
Returning as Richard Marston, Ed Stoppard is back as the newly elevated Foreign Secretary.
German Segal
German Segal will return as Vadim Trusov who is still working for the FSB but possibly in a different country this time…
Danny Sapani
Danny Sapani (Black Panther) also joins the cast as Charlie Francis, GCHQ’s Head of Security and Danny’s childhood friend. When the team find out there’s a mole, his mission is to find out both who and why!
Chloe Pirrie
You’ll recognise her from Black Mirror! Chloe Pirrie joins the cast as LT Colonel Roz Cavendish, seconded by Marston to GCHQ in the newly created role of Director of Rapid Response, a move that Danny sees as a threat to his authority.
Undeclared War season 2 episode guide:
If you're wondering how many episodes there are of The Undeclared War season 2, the answer is six! All episodes are now available to stream but we thought we'd give you a little debrief as each episode comes out on linear! PSSSST spoiler alert!
Episode one
In the fallout of Russian cyber-attack we see Danny thrown right into the middle of the chaos as he tries to get the Americans back on side with the help of Saara and the data shared by Vadim. Alongside this, the pair team up with security expert Charlie Francis to try and work out how Russia were able to get into the sandbox in the first place which soon sends them searching for a mole hidden deep within the organisation! And the final big plot of episode one? A huuuuge new threat emerges as Saara discovers Vadim is no longer in Russia and that was just the start...
Episode two
Welcome to Chinaaaa! As the fallout from the cyber-attacks continues, Danny is forced to take a fresh look at the case when Saara reveals that Vadim has been secretly communicating from China and claims the operation may go far beyond Russia. While Vadim works under constant surveillance, he risks everything to uncover what the Chinese are really searching for in the stolen data and find a way out.
Back at GCHQ, Danny, Roz and David begin to suspect an unprecedented Russia-China cyber partnership, while Charlie Francis steps up his hunt for the mole who helped the attackers breach the sandbox. But just as the team closes in on a suspect and Vadim's cover is blown, a dramatic escape and a shocking revelation leave Danny facing an uncomfortable possibility: the traitor may be far closer to home than anyone imagined...
Episode three
As the hunt for the mole continues, the spotlight falls increasingly on Barbara as long-buried secrets from her past begin to resurface. Through flashbacks to a disastrous MI6 mission in Hong Kong, we learn more about her relationship with former lover Nicky and the events that have haunted her ever since. But when the pair reconnect in the present day, Barbara is forced to confront a devastating truth about the man she thought she knew.
Meanwhile, Danny's suspicions about Barbara continue to grow and he becomes determined to find out exactly what she's hiding. But as he follows the trail, what he discovers leaves him shocked and raises even more questions about where Barbara's loyalties really lie...
Episode four
A dangerous new cyber threat throws GCHQ into crisis as a fast-spreading worm begins wreaking havoc across multiple areas of government. With the situation escalating rapidly, the Malware department is forced to join forces with Ross's team in a desperate race to contain the attack before it causes even greater damage.
Meanwhile, Barbara finds herself under immense pressure as the consequences of her past actions continue to close in. Struggling with mounting stress and increasingly erratic behaviour, she becomes obsessed with tracking down Nicky and uncovering the truth, even as the walls begin to close around her.
Episode five
As the devastating cyber worm continues to wreak havoc across government systems, Danny, Saara, Roz and the Malware team race against time to stop it spreading even further. With pressure mounting from the Prime Minister and fears the attack could spill over into allied networks, the team deploy a risky new plan that could finally turn the tide against the malware.
Meanwhile, Barbara finds herself under increasing scrutiny as Charlie's mole investigation uncovers more links to her past actions. As she desperately searches for answers about Nicky and the role he may have played in the conspiracy, Danny begins to uncover secrets she has been hiding from him. And with Vadim's rescue from China hanging in the balance, a tragic death, a dramatic escape and a shocking discovery leave the walls closing in from every direction.
Episode six
As the crisis reaches its dramatic conclusion, Barbara finally reveals the truth about her involvement in the cyber-attack and the devastating chain of events that allowed China to infiltrate GCHQ. Faced with evidence of a much wider conspiracy reaching into the highest levels of government, Danny risks everything to expose the truth before it can be buried for good.
Meanwhile, the race to stop the ever-evolving cyber worm enters its final phase, while Saara and the team fight to bring Vadim home safely from China. As arrests are made, secrets are exposed and loyalties are tested, the series builds towards a high-stakes showdown that could change the future of UK intelligence forever
The trailer for The Undeclared War season 2:
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When can I watch Season 2 of The Undeclared War?
You can stream all episodes of The Undeclared War season 2 now on Channel 4!
So make sure to add The Undeclared War to your Freely MyList and if you're looking for more shows to watch, why not check out the Freely TV guide.
