The Green party is holding leadership elections for the first time in its history, with Euro MEP Caroline Lucas running against former star of The Bill, Ashley Gunstock. In the second of a special two-part feature we interview both candidates to find out who will lead the Greens into the general election. This week: Caroline Lucas.
Leadership elections are always strange. You're presented with two or more people who inevitably share a broad political agenda but whose individual goals are markedly different. Sometimes it all comes down to management style and personal ambition - I mean, how much did Nick Clegg and Chris Huhne really have to differentiate them? Sometimes it comes down to beliefs.
The contest for the leadership of the Green party falls firmly in the second category. You have two candidates who believe in green issues, and who share most of their ideas about how to implement them, but they have fundamental differences over what the Green party should be. The contest between Ashley Gunstock and Caroline Lucas is about nothing less than how far activist parties can form themselves into viable electoral forces without compromising on their principles.
Last week, Gunstock explained how he was initially attracted to the party because of its grass roots approach to politics, and suggested a Lucas leadership would result in more central organisation along the lines of the three main parties. I put that to her.
"In terms of what he's saying about me, I don't think it's necessarily centralisation, but it's certainly about becoming more professional," she replies.
"There was a time when I first joined the party when people questioned whether elections should be the focus of our activity. If you join a party, you're saying you want a party political response to the challenges we've got.
"I think the party will always have roots in broader political actions. It's perfectly legitimate for politicians to engage in peaceful activism. I see myself very much as an activist as well as a politician. We want people to see us as politicians in a broader sense, rather than just men in grey suits."
So there you have it; more professional, more focused towards elections, but still rooted in grass-roots activism. A new kind of politician; respectable and still a protestor. Well, that's the idea anyway. These things have a habit of running away with you. If you get good results from becoming more respectable - maybe a couple of members of parliament for example - you might be tempted to make yourself even more respectable. And then one day you're so respectable you're not the same person you once were.
But Lucas has a very specific idea of the space she wants the Green party to take over. It's the space departed by Labour, the space the Liberal Democrats have always considered jumping into but never quite made the plunge: The Left.
"Left is your word," Lucas rebukes me. "I'd say radical progressive. We've been pigeon-holed into just being a party of the environment too much. We've put social justice at the heart of our record. We've been going out to the unions in recent years to communicate to them there is a party with the record they are looking for and it's not the Labour party."
I put it to her that union workers, those in industries which will be crippled - even eradicated - by a radical environmental agenda, might not be so happy to learn of the imminent extinction of their profession.
"Their industries are under threat from climate change - not environmentalism," she says. "The Green party has a clear message - the transition from high to low carbon economy has to have workers in the forefront of it.
"Given it has to happen one way or another, it can either be forced on us or we can manage it in the best way. Obviously it's frightening to realise your industry will change. But a post-carbon economy will need lots of skills and human power so it's very good news for a lot of workers. These industries will be more labour intensive than the fossil fuels they are set to replace."
It's an interesting argument, even a little radical. Certainly, it's a different way of looking at the political ramifications of climate change. But Lucas' route to achieving it is - and this was probably Gunstock's point - fairly orthodox. That doesn't make it wrong. But it does mean the Greens will lose some of their rebellious image.
"We need Green MPs in the Commons," she says simply. "We'll concentrate on Brighton Pavilion, Norwich South and Lewisham. We're already putting together the most professional campaigns we've ever had. We can build on that."
When the Greens decided to replace the post of principle speaker with a full-time leader, they made a conscious decision to become more media friendly, more electable, more concerned with talking to the country rather than themselves. They now have to decide how far down that path they want to go and what that means.
Does increased respectability spell the beginning of the end for radical environmentalism? Or can they achieve more by casting themselves increasingly in the image of mainstream parties, while still trying to retain a radical edge? It's a question many movements have had to answer. The Greens have until September to decide.