If the (brilliant) first episode is anything to go by, a certain Harry Pearce could well be the focus this time around, so when we visited the set with some other reporters we were determined to get some scoop from Peter Firth.
We've got some other chats coming up this week, but first read on to find out what Peter had to say about the new episodes (with some mild spoilers), Ruth, and why he doesn't think Harry will be killed off...
Where do we find Harry when the show returns?
"On gardening leave! Or just having had a couple of months out while his tribunal is convened to deal with his misdemeanour. We open with the tribunal, which is threatening him with a charge of conspiracy to high treason because - if you remember in the last series - there was a deal with Albany, the state secret which he traded for Ruth's life. They take a very dim view of that and sadly it has to be dealt with. But a situation arises whereby they need Harry, so he's temporarily reinstated for the first episode."
We've heard that Harry and the team have to forge new relationships with different countries like Russia.
"Yes, it's quite interesting. Again, a prophetic - it seems to me - storyline from the writers about the special relationship with the US, which seems to be deteriorating. But we do need friends and partners in the world and perhaps the Americans are not the ones we should be so pally with as they have such an atrocious foreign policy. So Russia is the obvious choice for Britain to align itself with - this isn't me speaking, this is the storyline speaking!
What about Harry's personal relationships - how do they develop?
"He doesn't have any, seemingly! The Ruth-Harry thing is entering a new phase, and it may be too late for them to proceed any further. They may have gone past the moment. And there could be somebody... I mean, Harry does have a past, and some of that is in Russia. He was stationed in West Berlin when he was with MI6, during the Cold War, during the 80s. And of course he had a life then, which could come back to haunt him."
Can you tease a little bit more about that?
"Well, Harry was in love with a Russian spy in the 80s but she was a double agent, Elena. She was working for Harry spying on the Russians. Elena marries a Russian politician and that is her cover so she spends her life undercover, basically."
Does Ruth find out about this?
"Ruth finds out in the first episode - I tell her. And it's the start of a new direction for their relationship."
How does the secret come up?
"Elena is in London with her husband, with the Russian husband. And part of their security detail is her son, who's with the FSB. I meet with Elena for a reason I won't tell you about, and he sees me talking to his mother, and then he finds messages that purportedly I've sent to her which would indicate that she's still spying, although she's not anymore - she gave up years ago. But the messages indicate that they're from me saying I need this information, I need that information. He finds these coded messages and assumes that his mother is still spying for the British against the Russians, but that's not the case. Someone is impersonating me and contacting her."
This is the tenth series of Spooks - do you think the storylines will live up to fans' expectations?
"The great thing about Spooks is it just keeps topping itself. It keeps getting more adventurous with the storylines, I think, and this year's no exception."
Is that the secret to its success?
"Partly. That's partly the secret to its success, but as William Goldman from Hollywood said, 'Nobody knows anything'. And that's true. Nobody knows why things are successful."
"I think the last series stands out for me - series nine - as being the best we've done. Although it didn't quite work, the end of it with Lucas North's departure. We ran out of money basically there and we were in the last couple of days of shooting and what we planned for him, we couldn't film. It was much more spectacular. So it didn't quite work. But dramatically I thought that was one of my favourite moments - the revelation that Lucas North, the long-trusted officer, was in fact not who he seemed to be at all."
So was there a pyrotechnic, explosive finale in mind at first?
"No, but it did involve a very tall skyscraper and a helicopter. But we couldn't afford the helicopter!"
Was Lucas originally going to survive?
"No, he was always going to die, but it was just how he was going to die. There was a version where Harry shot him on top of the skyscraper, and that involved a long falling man picture."
Has Lucas' betrayal and death affected Harry? Is he more jaded now?
"Yeah. I think that's inevitable. He's at that age when people begin to question their lives and the direction they're going in."
Has reaching the tenth series of Spooks made you reflective?
"I would have been reflective anyway. I think you get to a certain age and everything changes. Values change and concepts and direction, and I'm definitely at a crossroads. I think Harry Pearce most certainly is too."
Spooks is notorious for killing off characters - how would you feel if Harry was killed off?
"They won't kill Harry off."
Have they told you that?
"Never believe anything you're told by a production company, let alone MI5! But it's my belief that they would never kill Harry."
Would you like to see him go off and quietly retire?
"I'm not sure about that. It's not a tea shop in Devon! So I don't quite know. A let up from conflict would be appropriate, wouldn't it?"
And what's it like for you to see the cast members come and go around you?
"It's great. I've met everyone in the profession! Everyone who comes loves to do it. It's not just a job, it's not just a gig for people. They're invariably fans of the show and very happy to be in it."
"We've got Lara Pulver [as the new section D leader]. She's made us all pull our socks up. She's extremely enthusiastic and full on and filling quite difficult shoes to fill. It's a demanding role and she's all over it, so that's great. Max Brown, who joined us last year - gorgeous. Absolutely adorable. Much loved by the ladies. I've got a 19-year-old daughter at university and they're queueing up to visit the set, just to see Max. That's nice. And we have a new character, Calum. He's a welcome injection of a modern, casual attitude to national security. He's quite amusing. Very laid back and 'whatever'."
Some viewers will be surprised Beth isn't back - was that a decision Sophia Myles made?
"Yeah, I think she wants to be in America and who can blame her? She got married to an American and she's living in Laguna Beach. Hmm, Bermondsey or Laguna Beach..."
Is there any tension between Harry and Lara's character Erin?
"It's set up that there would be. They presume that I'm going to find it difficult to work with her because she's all business and new school rather than my rather laconic old school stance. But no, that hasn't emerged yet. We're getting on fine. I'm very proud of her character-wise as a potential replacement."
So is there no hope for Harry and Ruth?
"Love - you never know, do you? You just never know."
Spooks returns for its tenth and final series on Sunday at 9pm on BBC One.