As far as landmark moments in the green movement go, last Thursday was a pretty big one. The environment featured in the news as usual – there was a report saying the UK could power itself six times over with offshore renewable energy, and activists scaled London's BP building in protest at the oil disaster in the Gulf of Mexico. Both issues are pertinent to the greater cause, but the real sign of progress took place at the Houses of Parliament, where Caroline Lucas, the leader of the Green Party, was sworn in as Britain's first Green Member of Parliament.
When we meet at Westminster she is awaiting the call to be officially anointed an MP, a process that requires, after much hanging around, declaring loyalty to our head of state, the Queen. MPs can choose to say an affirmation over the traditional holy oath, but Lucas is obliged to swear a solemn and sincere allegiance to the Queen, an unfortunate piece of protocol for the leader of a party who would abolish the monarchy. "If you don't do it, you don't get to sit," she explains. "Until we get it changed, that's what you have to do. The people of Brighton Pavilion have elected me to do a job, and that's what I have to do to do it."
As for the hanging around, what's a few hours given that Lucas, in terms of her employment with the Green Party, has been hanging around for 24 years for this moment? The party itself has been waiting almost 40 years for a sniff of power.
Did she imagine it would take this long to get a single MP into the Commons? She laughs. "Absolutely not. I joined in 1986. There was a new awareness of the seriousness of the climate crisis but also of the benefits that could be gained by tackling it in a fair and effective way. And then we had our wonderful result in 1989, winning 15 per cent of the vote in the European elections. It was a lesson, actually, to see how temporary certain bursts of enthusiasm can be, and you can't take that for granted."
In terms of "bursts of enthusiasm", she says she is certain the current media interest in her will wane with time. She is, though, accompanied by an independent film-maker who is recording her first year in office. She brushes off his presence modestly, saying it might well come to nothing. But as Lucas, her party, constituents, supporters anywhere in the country and indeed across Europe and the world know, it has to come to something. Not necessarily the bust ups, back stabbing, bitching and in-fighting that makes good telly, but something that genuinely furthers the possibilities of green power in government and clears the way for more Green MPs. Otherwise, what's the point?
"There's a real urgency to what the Green Party's about," says Lucas. "Climate scientists say we have eight-to-10 years to get our emissions down, and if we miss that window of opportunity it will be a lot more difficult logistically to avoid the worst of climate change. That makes the next few years absolutely crucial."
The policy gains Lucas can make alone are obviously small (though not to be underestimated, as the Greens' record in Europe, where she was MEP for south-east England for a decade, and at the London Assembly, show). The Greens want emissions reduced by 10 per cent year on year. It's unlikely they'll get their wish on this and other policies. What Lucas can do is make sure that by the end of this Parliament, however long the coalition lasts, her party appears yet more electable – and that any last remnant of the Greens as a marginal group of mung bean idealist activists is erased forever.
"It's a huge responsibility," she says. "It's what keeps me awake at night. But it's a huge honour as well, and while I'm on my own in here, I feel very grounded by the support I have from my party and NGOs outside. I hope it's not impossible to demonstrate you can do politics without selling your principles."
Lucas wants "environmental justice for future generations," she says. But hasn't our new Prime Minister, David Cameron, just made the very same commitment, promising his Government will be the "greenest ever"?
"That's not very difficult, is it?" she says."Labour has been so appalling on the environment. The one thing they did was pass the Climate Act, but even then they got the wrong targets, and they didn't even have the right policies to meet the wrong targets. They weren't prepared to take real leadership on the issue and to use the same kind of political commitment they brought to the Iraq war. The fact Tony Blair chose not to put his political capital behind climate change but went for something as nasty and disastrous as Iraq is a real tragedy. He failed to see he could have made his mark in a positive way."
That said, she's no cheerleader for the new coalition. She dismisses Cameron's promise of green leadership as rhetoric and part of the continuing process of "decontamination and rebranding" of the Tory party. One of the biggest coalition compromises, the Liberal Democrats' agreement to a referendum on the Alternative Vote (AV) rather than Proportional Representation (PR), affects the Green Party as radically as any environmental policy. "I'm desperately disappointed that the zeal for opening up this place so people's voices really count, by introducing some form of proportional representation, has been lost," says Lucas.
PR would have given the Green Party a much better chance of winning more seats in future elections. "This whole system is set up against smaller parties. Not just the electoral system but the media as well. If you're not at Westminster, you're not really there in the media's mind." To be fair to the political media, there are well over 600 MPs to chase around the country, so following up anyone without office is not always possible. But Lucas thinks it was probably media coverage, specifically the leaders' debates, which caused her colleague Adrian Ramsay to lose out in Norwich South to the Liberal Democrat candidate. "In terms of the national picture, the Lib Dems were presented as the alternative," she says. "If they hadn't had so much extra profile it would have been very different. It gave the impression there were no alternatives on a whole range of issues, from cuts to public services or Afghanistan. By simply turning a two-party stitch up into a three-party stitch up, the media did the British public a disservice."
Even more disappointing for Lucas was the fact no party made the environment a priority in their campaign. It barely got a mention. No doubt due in part to the fact that, in an economic downturn, politicians believe the only thing voters care about is money. The other problem is that being green is seen as a lifestyle choice that demands a huge amount of effort and substantial sacrifices. Lucas points out that building a green economy will create jobs in all areas, from green energy provision to a quality self-sufficient food system. "Everyone has associated environmental changes with a loss of quality of life. There are lots of things I find hard, but that's because we don't have an enabling policy framework to make it easy for people to live a green lifestyle. You can't blame people for not leaving their cars at home when there isn't an alternative."
When Lucas joined the Green Party it didn't look like much of an alternative. It has been slow to modernise – only electing Lucas as the sole party leader in 2008 – and accept that to win seats in Parliament it has to structure itself and behave as mainstream parties do, however that sits with its own views of how politics should be done.
Lucas found the Greens "via lots of activism and organisations like CND". She believes there is always a role for non-violent direct action – "when you're dealing with something as potentially serious as runaway climate change and you've got a government that doesn't listen, taking those actions does put the issue on the agenda" – and has been arrested for protesting outside the Faslane nuclear base and at Westminster. But as a former press officer she knows that how is she personally is perceived, as her party's figurehead, is as important, if not more so, than policy. As such, her gentle manner, understated dress and modest but forthright way of engaging with the issues is a refreshing counter to our brusque, bully boy way of doing political business at the moment.
If this approach continues to work, the electorate's opinion of her could change in line with that of her own parents, Conservative voters. "I think they felt the Green Party was not a very serious way to be spending your time," admits Lucas of their initial reaction to her chosen path. "To be fair to them, once I'd got into the European Parliament they decided it was a bit more respectable that they'd thought."