We're seated in a pub forecourt in Vauxhall, a hedge separating us from a noxious South London thoroughfare, and Humans actress Emily Berrington is demonstrating how a robot "synth" would stand up from a chair. “You have to sit well forward so your weight is almost entirely over your feet”, explains Berrington, who plays renegade synth Niska in the hit Channel 4 drama.

“Also you have to think of where you want your head to be when you are up, so you put your head into that position before standing. They move with the greatest of economy because they're battery powered and any extra movement drains your batteries. Also they work with a hydraulic system so there's no effort with their movement... no muscle power”.

Emily Berrington and her fellow actors play robots in Humans

Berrington and her fellow actors playing the robots in Humans – Gemma Chan, Colin Morgan, Will Tudor and a bevy of newcomers in season two – attend a so-called "synth school" run by choreographer Dan O'Neill, who also attends the shoot to correct them when their movement becomes too human.

“I literally can't talk without moving hands”, says Berrington, gesticulating wildly as if to prove the point. “To begin with I was worried that all my performance would disappear, but actually it forces you to think more, have real thoughts that you can't 'show'. When I was doing the scenes with William Hurt last year, who was playing a human, that was what he was doing anyway. He wasn't doing sad faces and wringing his hands, he was just thinking. I think Humans has massively improved me as an actor.”

In last week's opening episode of Humans (spoiler alert) we found Niska, a semi-conscious synth, hiding out in Berlin with a copy of the code that "awakens" the robots, and deciding whether giving self-awareness to the hundreds of millions of robotic drudges across the world is morally the right thing to do.

Niska is also, of course, on the run, having acted as a one-woman synth vigilante during series one. Forced to work in a brothel, she murdered an elderly client with fantasies of mistreating a young girl, before going on the rampage with a metal bar at an underground "smash club" in which humans paid to beat up robots.

“They gave me a soft rubber bat and said 'do whatever you want with it'," says Berrington. “I was buying a flat at the time and going through all the difficult things of the vendor's solicitor not getting back to us and had a wonderful day bashing people up with a rubber bat, thinking of them as estate agents and vendor's solicitors.”

The Humans actress considered a career in politics before acting took over

How did she feel about playing a robotic sex worker? Were her scenes hard to film? “The poor guys who had to come in and do those scenes... I felt sorry for them”, she says with a laugh. “I found the whole sex worker thing really complex because part of me was thinking 'oh, well, at least it's not humans having to do it'. But on the other hand it was legitimising what maybe shouldn't be legitimised just because you're doing to something that can't feel? Is it the same as doing it to a fridge, does that make it okay?"

Hopefully it is clear by now that Berrington is thoughtful and articulate, and that acting is just one of several careers that might have opened up for the 30-year-old from Oxford. The daughter of social workers who went on to run a training business for the public sector, her sisters Amy and Katie are, respectively, in cancer research and journalism (at Vogue, and, no, Berrington didn't recognise the depiction of the magazine in the recent BBC2 documentary, Absolutely Fashion), while her brother runs his own business in Abu Dhabi.

Berrington herself studied geography at King's College, London, writing her dissertation on “the economic collapse of Argentina and the resulting rise of co-operativism”, before beginning work for the Labour Party as a case-worker for MP Siobhain McDonagh. “And before that I did an internship with Margaret Hodge when she was Secretary for Culture and Sport”, says Berrington, who loves politics more than Westminster.

“I remember thinking that it was the first time I had been anywhere that felt like a very gendered place... a male-heavy place... an older male heavy place”, she says. “At the time I wasn't confident enough to assert my own status in my professional role, but I'd like to think that if I'd stayed there I would have continued to have a career in politics and in the Labour Party.

Berrington is also starring in Dead Funny at the Vaudeville Theatre (Alistair Muir)

Perhaps challenging Jeremy Corbyn for the leadership? “Maybe”, she laughs. “It's a tricky time now, in all honesty, and I've been in such a muddle about it. But I still feel very much part of it.”

Her role in the Inbetweeners movie sequel, in which she played the unfortunate crush of Simon Bird's character Will, led to a phone-call from the Labour Party press office. “I loved that I'd found a way to combine the two things I wanted as a career so I badgered them from then on. And I gave a speech at the Labour conference last year.”

She also travelled across the country with Ed Miliband during the 2015 election, introducing him at Young Labour gatherings – somewhat ironically since her long-term boyfriend (they've been an item since drama school), Ben Lloyd-Hughes, played the former Labour leader in the 2010 Channel 4 satirical drama-documentary, Miliband of Brothers.

In Humans Berrington plays Niska, who is on the run and forced to work in a brothel

We're meeting in Vauxhall because she is rehearsing nearby for her role in the revival of Terry Johnson's play 1994 Dead Funny. Johnson is currently being interviewed by another journalist elsewhere in the pub. Berrington appears alongside Ralf Little, Steve Pemberton, Rufus Jones and her Humans co-star Katherine Parkinson. “My character Lisa is married to Vic, who's played by Ralf Little, and we're part of a society called the Dead Funny Society which is a group of people that loves the comedians of the 60s, 70s and 80s... Morecambe & Wise, Tommy Cooper and all of those. And it's set on the night that Benny Hill died in 1992.”

In the meantime she has acted with Roger Allam in a film adaptation of Stephen Fry's novel Hippopotamus, which she shot last year and somewhat ominously doesn't expect to be released until mid-2017. (“Apparently Stephen saw it recently and liked it, so it's been green-lit by the most important person”, she says.) Right now she has a train to catch to Wiltshire, where she'll be spending her final free weekend for quite a while.

As we walk together to the tube station she tells me about other pertinent issues raised by Humans. “I've been reading a lot about what the internet does to our brains”, she says. “I mean I literally can't get anywhere now without the map on my phone. I used to use an A-Z when I first came to London and now I really struggle because there's no dot to show where I am. And I think that part of my brain doesn't work any more.” Never mind, I'm thinking, because there are plenty of other parts that do.