Whilst in the midst of filming the new episodes, Romola told Digital Spy all about the changes in her character's life, the show's new cast members - including Peter Capaldi and Tom Burke - and her thoughts on whether we could see a third series of The Hour...
How has it been for you coming back to The Hour for series two?
"It's been great, thanks - it's been a really fantastic experience for us. I'm so happy we got the second series."
How has Bel changed since the first series?
"I think she's more used to being in the job now, so that's maybe given her a bit more gravitas and greater professionalism. At the beginning of the show, Freddie isn't there and he's very much the fire in her belly, so I think she's slightly missing her other half."
So she's more established and respected in the halls of the BBC now?
"Yeah, the first series took place over two months and it's been a seven-month gap since then. She's been in the job for almost a year, so that's quite enough time for her to really become used to the authority of her job."
Freddie is away initially but what is his relationship like with Bel once he returns?
"It is difficult, because there's acknowledgement that there's a sort of love affair in their relationship. But the 'on again / off again' nature builds to a head through the course of the series. So I guess it's complicated!"
What about Bel and Hector - where do we find them this series?
"Well, Hector is definitely no longer the man in Bel's life and the relationship they had in the first series is very much over. So I think that they've got quite a nice relationship now - they've had a fling but they're grown-ups and Bel's very happy to let that be ancient history."
Hector gets involved in a scandal this series. Is Bel involved in that at all?
"Well, the themes of the show have changed this year. Vice and the Soho underworld are the main concentrations of the show along with CND and nuclear disarmament. So all the characters are involved in those plot lines, but Hector becoming personally involved in a kind of vice ring is the thing that kicks off that storyline."
Bel's also got a new relationship with Bill Kendall (Tom Burke)...
"Yes, ITV have launched a show that is being directly pitted against The Hour called Uncovered, and it's very much in the great tradition of ITV / BBC rivalry.
"Abi makes a great job of playing on that because Bel's other half - the producer of Uncovered - is this very attractive new guy called Bill Kendall. They sort of start a relationship, so that becomes a great work vs love life conundrum for Bel."
Peter Capaldi has also joined the cast - what's it been like working with him?
"It's been amazing. I don't know how Peter's done it because he's also appearing in the West End at the moment, in The Ladykillers. He's become a sort of acting legend on the set of The Hour - we're always moaning about being really tired and the really long hours and he goes off and does a 3-hour really physical comedy every evening! So he's an amazing actor and it's incredible that he's been able to do the show."
How does his character Randall compare to Clarence and the old regime?
"I think Randall's representative of a different generation in that he's much closer to Lix (Anna Chancellor) as he was a journalist for a long time and has a similar background to Lix - they would have been the people who reported on the Spanish Civil War and the Second World War. It's much more of that active, out-in-the-fields school of journalism. So he's much more on the side of the team, I guess."
This is obviously your second year making The Hour, but are you still amazed by the show's style and period detail?
"Yeah, I always feel like costume and production design in this country is really amazing and I think that we're so lucky that when we do television we get people of the quality of Eve Stewart, who's our production designer - she makes huge films and works with incredible directors, but is prepared to do TV as well and so we get this incredible quality of work.
"I really have to say that I think the sets on The Hour and the art department and the attention to detail with our props is incredible - all our telex machines work and our telephones work. That kind of element to it is fantastic and has been a real joy. It's brilliant when you go on set and you're like, 'So I'm getting a telegram - how are we going to fake this?' and they're like, 'No no no, the telegram works!' - it's been great."
Last year before the show started, there were comparisons made to Mad Men - do you feel like The Hour has its own identity now?
"I think it always had its own identity. I think the comparison only became a comparison because people asked that question, so it's difficult because if you answer it, you perpetrate the same kind of concept. And I think it's not useful because they are set in the same period, but really any kind of comparison between the shows ends there.
"Mad Men has a much much longer format because of it being an American show - it's a drama, it's primarily about capitalism, a sense of advertising. Its themes, its interests, its genres, its format - they're all different. As much as I love Mad Men, it doesn't really do either show any favours to compare them when they're clearly completely different."
Do you think The Hour could keep picking up with these characters every few years - into a third series and possibly beyond?
"I don't know - I've never done a series before, so I have no idea really. I mean, I always knew that there was a chance of doing a second one, but I don't really know how many audience viewers you need to do a third one or if Abi will be interested in writing a third series.
"I mean, potentially you can do these things for years - obviously we know from American television that we can do endless seasons of shows like this. I don't think the format of this show lends itself to running for ten or fifteen years, but hopefully we'll do some more."
The Hour series two begins this Wednesday (November 14) at 9pm on BBC Two.