The first thing I notice when I meet Sian Berry is the whiteboard.

Written across it in different colour pen are numbers – various calculations a la A Beautiful Mind. The complicated maths dominating one side of the small office room is an insight into how the former co-leader of the Green Party does politics.

“We were the only ones paying attention when [Sadiq Khan] published his draft budget,” says Berry, who had just spotted that the mayor of London was planning to freeze fares – but hadn’t announced it. “We pay attention to everything the mayor does. We look for gaps, we look for opportunities. We were looking very closely at that number.”

This attention to detail is what Berry hopes she can take from her local government role on the London Assembly into Westminster. The longstanding campaigner was selected last year with 71% of first preference votes to stand in Brighton Pavilion, after MP Caroline Lucas announced she was stepping down. This is the only seat the Greens have ever held in the House of Commons, and if Berry were to win – as she is expected to do – she would help usher in a new era for the party.

“It’s incredibly exciting,” she tells me from City Hall in east London. “I’m not pleased that Caroline is leaving, but I was so pleased that she had the faith in me to ask me to do it because it’s such an important job.”

It’s been a long time coming for Berry. She joined the Greens in 2001 and first stood for election in 2002, but it wasn’t until 2014 that she was elected – as a councillor in Camden, north London. It was a position she held for almost 10 years until stepping down in October to focus on Brighton. Alongside that, in 2016 Berry was also elected to the Assembly, the body tasked with scrutinising the mayor of London, where she has campaigned for increased funding for youth services, and of course, studied the numbers.

Campaign issues

If she does enter the world of national politics, she will likely be doing so in a Parliament that looks very different than it does today. The Conservatives are currently heading for wipeout, polling around 20 points behind Labour, as they have been doing steadily since Liz Truss’s disastrous mini-budget.

“[The Conservatives] have completely given up,” says Berry. “Really, they've abandoned all credibility, and are just flinging ideas out.”

The current state of the Tory party reminds her of Boris Johnson’s behaviour while London mayor – coming up with wacky, expensive ideas like the now-infamous (and scrapped) Garden Bridge: “Like: ‘I had a bright idea in the cab on the way here and now I’m going to announce it.’”

The Green Party, which stands on a platform of socialist fiscal policies, left-wing social ideals and of course, a strong climate change agenda, has been polling steadily at around 7%.

And it’s the climate policies in particular that are resonating amid a relentless stream of frightening statistics about global warming.

North of 20 million people a year are being displaced because of climate change – and it’s getting worse. The world has just seen its first full year in which average global temperatures tipped over the 1.5°C limit set by the Paris Agreement in 2015. Meanwhile, the government is ploughing ahead with new oil and gas licences, and basing policies around the plight of car owners rather than the lifespan of the planet.

“None of the other parties are making it the priority it should be,” says Berry. “This is despite the fact that all the temperature charts for the world – air temperature, sea temperature is particularly terrifying – they’re literally off the charts.”

She adds: “We’ve gone over 1.5°C, which we knew was a tipping point, for a whole year. We could be in a situation of genuine climate crisis much sooner [than we thought].”

It’s not just the government who Berry sees as failing on climate policies. We speak a few weeks after Labour scraps its £28bn green investment pledge, much to the anger of climate campaigners. “The need for Green MPs to be [in Westminster] so clear,” she says.

It’s one of the issues coming up on the doorstep, Berry says. She has been spending all her time outside of City Hall down in Brighton, getting a feel for the issues in the seaside town. As well as the climate, there are other key concerns that people want to talk about – access to healthcare, cuts to youth services and, inevitably, housing.

“You cannot knock on a renter’s door without them bringing up the cost of rent,” she says. “There are so many people. When you knock on the doors of people who are living in social housing, damp and mould is being put in front of my literal eyes. There’s a crisis in Brighton on the condition of social housing – just as there is in every part of the country – as well as overcrowding, access to council homes. Just as it is everywhere.”

Do landlords have too much power? “Yeah,” says Berry, without missing a beat. “Without rent controls, without the power to demand standards and legal compliance from your landlord, and with Section 21 [no-fault evictions] still on the books, you don’t have any real rights and that gives your landlord more or less all of the power.”

There are other solutions: “We should be building more houses, but we should be building more council homes and social housing by a massive, massive preference. That's not what’s going on at the moment.”

Transphobia

In 2021, Berry stepped down as co-chair of the Greens, explaining in an openDemocracy piece at the time that her trans-inclusive beliefs were not compatible with the party’s decision to hire a spokesperson who did not share those views.

That spokesperson, Shahrar Ali, was later fired from the role. Ali took the Green Party to court over the decision, arguing he had been dismissed because of his “gender-critical” views, a protected belief under the Equality Act. As part of his case, he accused Berry of discrimination, quoting the openDemocracy interview.

A court judgement in February found proper procedure had not been followed during Ali’s dismissal, and awarded him £9,100 in damages. Crucially, however, the court acknowledged the right for a party to dismiss a spokesperson if they do not support the position of the party.

How does Berry feel about the judgement? “I find it interesting because it did to some extent say I was correct,” she says.

It is also vindication of her decision to step down at the time. “[Ali] had demonstrated repeatedly that they did not agree with our policy that was positive towards trans people, and was severely antagonistic towards the members who wanted to make sure that the party stood by its values,” Berry says.

The case symbolises an internal battle the Green Party is having over its position on trans rights. It is a trans-inclusive party, but some members don’t believe it should be. Is it still struggling with this problem?

“It is still an ongoing issue,” says Berry. “I wish we’d been able to deal with transphobia sooner. We weren’t able to keep it from being quite a big part of a lot of Green Party spaces. That made a lot of people really upset and was unfair and discriminatory towards our trans and non-binary members.”

Does UK politics have a transphobia problem? Berry agrees when asked if the Conservatives have shown themselves to be transphobic, but says things are a little less clear with Labour: “There are people at all levels in the Labour Party who are speaking in a more intolerant and transphobic way and the Labour Party is not choosing to deal with that.”

At this point, Berry stresses she does not want transphobia to dominate the interview, telling me that publicly and privately it has taken up a lot of energy. Indeed, the court documents show that issues raised in Berry’s 2021 openDemocracy interview were later also subject to internal complaints, which Berry has been cleared of. Not that she wants sympathy – she is instead keen for people to focus on the difficulties those groups face. Transphobia in the UK is dominant in the media and politics; amplified by a small group of loud voices. There are consequences to stoking hatred: Last year, in February 2023, trans schoolgirl Brianna Ghey was murdered by two schoolmates in a park.

So Berry draws a line under the topic: “It's not a subject I thought when I came into this job would need this much debate. It just seems so obvious. We were moving in the right direction and I thought that people with all kinds of differences would have more rights in the future, and we’d be pleased about it.”

A Green surge?

Berry is under no illusion that the Greens are anywhere near a majority in Westminster, but says the party’s ambition is to play a similar role in the Commons as it does on the Greater London Authority, where she is one of three Green Assembly members.

“In the current system,” she says, “we’re looking to become the most influential opposition party, like we are in this building.”

At a time when politics seems so bleak – mired in scandal, policies that offer crumbs of support for the most vulnerable alongside tax breaks for the wealthy – the Greens come with the more radical message of hope. It’s one, arguably, the party can hold with little expectation of achieving real power. Or could it? I ask Berry whether we might see a Green government in my lifetime.

“I truly believe there’s a progressive majority in this country and that if we had proportional representation we’d have parties on the broad left able to form a government,” she says. “If you look at the exponential growth in our councillors…then who knows?”