Green Party co-leader Caroline Lucas. Jack Taylor / Getty LONDON — I meet Green Party co-leader Caroline Lucas inside Portcullis House, a sort of vast Parliamentary greenhouse in which MPs and their aides drink coffee, chat and brief journalists.

In the daytime, it is bright and airy but by late afternoon in the winter the lack of artificial lighting means it is shrouded in semi-darkness. I grab Lucas as she searches for me in the gloom.

Lucas is friendly and immediately engaging. Unusually for a prominent politician, she is not accompanied by any aides or minders. We sit down and begin what turns into a long and expansive conversation covering everything from progressive alliances, to homeopathy, to her disappointment in Jeremy Corbyn.

We begin by talking about her upbringing in a reserved middle-class family in Worcestershire.

"My family were small-c conservatives," she tells me.

"But the miners' strike and the Falklands were things that kind of came crashing into an upbringing that had been pretty conservative and raised a lot of questions about how does the Daily Mail, which was the staple newspaper in the house, how does it really make sense given what I could see was happening in the world."

When Lucas got her hands on Jonathan Porritt's book "Seeing Green" it changed everything.

"Essentially, what it did was put forward an approach which made the links between the same kinds of world view that means that men have patriarchal rule over women and that the environment is being exploited and that nuclear weapons are seen to be a realistic and reasonable way of sorting out global conflict.

"So, what I found in that book was a sense of the connections between all the different issues which I had been concerned with but had not recognised the links between them until that point."

Direct action

Lucas became involved in a number of environmental and women's groups and even took part in illegal "direct action" during protests. One such action was the "Snowball campaign" in which protestors, including Lucas, cut the wire fencing at military bases in protest against nuclear weapons. It is a practice she has continued to adopt, including in 2013, when she was arrested alongside her son, for their part in a protest against fracking in Balcombe.

"I accept that as an elected politician I have a number of other tools that I can use to bring about change but I would also say that the Green party remains committed to appropriate non-violent direct action and I think it is a tool in some cases that is legitimate," she insists.

It is not a view that her Daily Mail-reading parents share, however.

"I think that they thought it was something I would quickly grow out of and were slightly embarrassed about. But I think that once I was elected that gave it a level of respectability that has since fortunately helped.

"But when my father got a phone call at the rotary club saying I have just been arrested at Balcombe then that didn't go down very well."

When my father got a phone call at the rotary club saying I have just been arrested at Balcombe then that didn't go down very well."

Lucas quickly rose to become a star of the green movement, before being elected as Green party leader and their first MP, winning the seat of Brighton Pavilion. At the time many commentators suggested that the Greens were a major threat to the then Miliband-led Labour party. However, Lucas was concerned about losing her seat, then held by just over a thousand votes, and stood aside to embed herself in her constituency.

Lucas has managed to increase her majority, but the rest of her party have failed to do as well. Her replacement as leader, Natalie Bennett, failed to achieve the same level of success as Lucas and the party has gradually slipped both in the polls and the national conversation. The election of Jeremy Corbyn, who shares many of the same views as the Greens, to the Labour leadership, is widely seen to have squeezed their electoral appeal as well as claiming their members.

The Corbyn-squeeze

Lucas admits that Corbyn has had an effect on the Greens.

"When he was first elected there were some Greens who joined Labour, that's no secret," she says.

"But our membership has stabilised and actually they're coming back now because they've been disappointed that Labour as a whole hasn't lived up to the kind of vision and leadership that Jeremy was setting out."

Disappointment is a word that crops up again and again as we discuss Corbyn.

Lucas has worked closely with the Labour leader over the years. The two were Chair and Vice-chair of the parliamentary group of Campaign for Nuclear Disarmament (CND) and she says she still has "a lot of respect for him" — but suggests he has been taken over by his own party machine.

"Unfortunately the position with Labour right now is we don't know what their position is. Jeremy was pushed really hard on the Marr programme [last week] about Copeland and his position on nuclear. I understand the dilemma that he faces but it is desperately disappointing that you get somebody with those views in a position of influence and he is unable to bring the rest of his party with him."

She suggests that Corbyn's "heart isn't really in" the party's position on Brexit either.

"I think on Brexit overall Labour has been deeply disappointing. I think giving the government the green light on triggering Article 50, saying they would not under any circumstance vote against Article 50, handed away far too much to the Conservatives and any sort of leverage they had on that was gone.

"On freedom of movement it was incredibly disappointing to see Jeremy dealing with the pressure he was undoubtedly under which meant that he made three U-turns in one day because actually, you could tell that his heart just wasn't in talking about controls on freedom of movement.

You could tell that [Jeremy's] heart just wasn't in talking abut controls on freedom of movement

"But that was the position he has been forced to take within his party."

Lucas and the Greens take an unashamedly pro-immigration position. However, it is telling that even Lucas is keen to talk about dealing with voter concerns about the issue.

"It is more important than ever that there is a Green party out there which is unequivocal about saying that we will stand up for the principle of freedom of movement. We believe not only that it is good for the economy but it is good for the society, it is good for our communities.

"But that doesn't mean to say there aren't ways that we can try to reduce the impact of sudden movements of people in certain areas."

I ask what she means by this.

"If you start off from the position that immigrants actually bring more economic value than they take out then let's make sure that value is concentrated in the areas where they're moving. So all I'm saying is let's put in some of the resources that those migrants — I hate the word migrants — those EU nationals, are bringing in with them."

Doesn't this sound an awful lot like Labour's migrant impact fund?

"I think that phrase is an unhelpful one because it immediately frames migration as a problem. But yes that's the basic idea."

She tells me that, unlike Labour, the Greens do not believe there will be "masses of opportunities from Brexit." Instead, she thinks it will be a "disaster for the environment, for universities, and for business."

For these reasons, she says the chances of her voting to trigger Article 50 in March are "very low."

"We are saying that if the kind of Brexit on offer looks as if it is going to be deeply damaging to the country, to my constituency and to the principles the Green party has always stood on then I don't see how in good conscience we can support that."

Are the Greens anti-science?

I don't see how in good conscience we can support [triggering Article 50]"

One allegation often levelled at the Greens is that they are anti-science. Their positions on issues like genetically modified crops have led to them being labelled as Luddites, while Lucas herself has been criticised for signing a parliamentary motion supporting homeopathy. I ask if her position has changed since.

"I think that EDM [a parliamentary motion Lucas signed on the issue] has been widely misconstrued," she insists.

"That EDM wasn't saying bring about homeopathy tomorrow. It was saying let's apply an evidence base to homoeopathy as we do to other medicines so I think the Green party remains pretty open."

Widespread evidence that homoeopathy does not work, or at least is only as effective as a placebo, does not seem to have convinced either Lucas or the Greens.

"We want to see a stronger evidence base," she insists. "Many people in homeopathic professions would say that the way the evidence is being used is not fair. It is not measuring like with like.

"It is not a major part of our policy," she adds, perhaps in anticipation of the criticism.

I ask if she's ever used it herself. She pauses.

"Yes I have."

Did it work?

"I can't really tell you whether it worked or not because who knows what would have happened. There wasn't a counter-factual to it."

We go on to talk about climate change, for which the evidence is overwhelming. She says she is concerned that Donald Trump will reverse much of the progress made by former-President Obama.

"Trump is surrounding himself with so many climate sceptics and when he himself says he thinks climate change is a Chinese hoax then there are real concerns."

She says she fears Theresa May will also sacrifice environmental protections in order to get a trade deal with the new US president.

"I don't think there's going to be any appetite in the Trump administration to build in any kind of environmental protections into a trade deal. And if our government are so gung-ho about getting a quick US trade deal to demonstrate their post-Brexit success then the environment will certainly be a loser in that process."

Lucas is an articulate speaker, fiercely intelligent and clearly highly principled. Yet it's hard to see how she and her party fit into this new world of populist politics as typified by Trump and Bernie Sanders in the US. She disagrees.

"In a way, there are opportunities here for the Greens because what we're seeing is a massive disillusionment with politics as usual and with politicians' who are out of touch with their constituents. I think the Greens do politics differently and so there is an opportunity for us to cut through," she insists.

"To the extent that Bernie Sanders was about building a movement of people where challenging things that up until then were unchallengeable, then absolutely we want to be seen in that mould."

Progressive alliances

Yet the polls, some of which out her party as low as 2%, are not encouraging. Whether it is the Corbyn-squeeze, or the rise of right-wing populism, the Greens are currently struggling to find a route into the national conversation. For Lucas, the key to both her party's revival and the success of progressive parties in general, must come from forging progressive alliances.

The party already trialled this in the recent Richmond by-election where they stood aside and helped the Liberal Democrat candidate Sarah Olney defeat Zac Goldsmith. However, in Copeland, where Labour face a tough battle to hold onto the seat against the Conservatives, the Greens have decided not to step aside. I ask her why not.

"There was a consideration but that consideration wouldn't have taken as long as it might have done given that the candidate Labour are going to field [Gillian Troughton] is pro-nuclear and that was a big problem. And I imagine if there had been any idea of a candidate being anti-nuclear and pro-electoral reform then there might have been more scope for discussions."

But surely parties cannot agree on everything in a progressive alliance? Where do you draw the line?

"Well it will be different in different constituencies and that is appropriate because what a progressive alliance is not and what it should not be is some sort of backroom deal between parties which is then presented. Ideally you get local communities involved."

Last year Lucas took part in a fringe event at the Labour party conference about electoral reform. She says it was "standing room only" event and suggests she has had a number of conversations with Labour MPs "both on and off the record" about forging an alliance between the two parties on the issue.

"I think there is an appetite that goes well beyond their public position on this," she insists.

She picks out Jonathan Reynolds on electoral reform and Clive Lewis on progressive alliances, as two figures she believes the party can do business with.

"Clive Lewis has been very outspoken and very brave frankly in his support for a progressive alliance," she says.

However, it is an idea that has met resistance from Corbyn himself. I ask her why she thinks this is.

"I think unfortunately working with others can sometimes be perceived as a form of weakness and obviously he is under a lot of pressure now to demonstrate that his leadership alone can lead Labour to a victory at the next election. But I think probably even he, in his private moments, would reflect that it is going to be immensely difficult on their own [to win] and I think more and more people around him are coming to that same conclusion."