By Brian Wheeler
Political reporter, BBC News
Derek Wall must be the only political leader to have been banned from every Tesco supermarket in Britain.
This fact was announced with a flourish by the Green Party when Mr Wall became its "male principal speaker" - the Greens don't do leaders - in November.
But Mr Wall looks a little bashful when I bring it up. He has never tested the ban out, he says.
He is very much a peaceful protester. Apart from anything else he practises a form of Zen Buddhism.
The Tesco ban came after he was photographed up a tree in Bristol, where he was campaigning against plans to open a new store.
Mr Wall is not a fan of Tesco, or any other multinational come to that - and he wants Green Party activists to get more involved in protesting against them.
In a sign of changing political times, he has even given a talk to his local Conservative association about what he calls the company's "Tescopoly" - an experience he describes as "interesting".
It seems this is a good time to be in the Green Party.
Far from making the party redundant, the apparent conversion to green politics of the two largest parties at Westminster - after Tory leader David Cameron took up the climate change cause - appears to have sparked new public interest.
According to a recent Guardian/ICM poll, Conservative voters, in particular, seem to be taking notice of the Greens.
Asked to name one or more other parties that they might support, Conservatives polled were much more likely to choose the Liberal Democrats or the Greens than parties such as UKIP.
Sian Berry is the Green Party's other principal speaker
Some 32% of Tories say they might vote Lib Dem and 19% say Green.
When we meet in a Kensington pub, round the corner from the college where he works as an economics lecturer, Mr Wall is beaming about another poll which, he says, shows the Green Party's vote has gone up from 1% to 4%.
The party has since claimed its support has reached 5% of voters.
You have take comfort where you can when you head a small political party in Britain.
It can be a thankless task - the first-past-the-post voting system at general elections is particularly unforgiving.
The Greens received 6.3% of the vote in the 2004 European elections, which uses a form of proportional representation, but only 1% of the vote at the 2005 general election, with 256,020 votes, after contesting 200 of the 646 seats.
The Greens clearly still have a mountain to climb if they are ever going to have an MP at Westminster.
Mr Wall's predecessor, Keith Taylor, came closest last year in Brighton Pavillion, where he came third with 22% of the vote.
But Mr Wall believes the debate is moving the Greens' way and he wants to build on the party's steady progress at the ballot box - they currently have close to 100 local councillors and two MEPs.
Although it is a separate party, the Greens in Scotland have high hopes of making progress at next year's elections - perhaps even governing in coalition.
That would give the English Greens a major boost, says Mr Wall.
"What we need in politics is vision and I think that is one of the reasons that the Green Party vote is going up.
"People are disappointed with cynical, PR-based politicians, who have no vision.
"But you have to combine the vision with practical steps to get there."
With his talk of taking on big corporations and concentrating on "general well being" rather than just profit, David Cameron seems to have cribbed much of his rhetoric from the Green Party - they even suspect the Tory leader may have been taking a quiet peek at their website.
But Mr Cameron's concern about the environment is skin deep, says Mr Wall.
There was no mention of climate change in the party's 2005 manifesto, he argues, which was largely Mr Cameron's work.
"Cameron has not got the practical policies. It's like Bush talking about Compassionate Conservatism. He's softening the Conservatives' image so that people will vote for them, but when he gets into power we could see policies which are very different from the rhetoric.
"We get feelgood rhetoric. I don't think we will get feelgood policies."
But Mr Wall reserves his real scorn for Chancellor Gordon Brown, the man most people expect to take over as prime minister from Tony Blair.
The chancellor's conversion to green politics has been very half-hearted, he argues, and his "joyless" obsession with economic growth counterproductive.
"Gordon Brown is the finest opponent the Green Party could have. He's the antithesis of green politics.
"If something is good for corporations, if something is good for business, that's good for Gordon Brown.
"We have got to look at it the other way round, what's good for people, what's good for the environment.
"He's got this dour, puritan politics. I looked at the pre-Budget report and I think we will actually look back to Blair - Blair has been terrible - but Blair will look better than Brown, if Brown ever becomes prime minister."
He also has little time for the Lib Dems, which he says have been taken over by "market liberals" such as deputy leader Vince Cable.
Mr Cable is a former chief economist at oil giant Shell - another company on Mr Wall's list of bete noires.
Does he think his anti-corporate stance will alienate voters, many of whom, after all, work for big corporations?
"Look at the world we've got. We can't say that people who run corporations are villains but corporations have to make a profit for their shareholders and the problem with short-term profit is it does not give us long-term sustainability.
"All the time, the radical message is the economy and growth have got to serve us and not the other way round."
He is keen to stress the "practical steps" the Greens would take if they ever got into government such as massively increasing the amount spent on renewable energy and cutting carbon emissions by 6% a year.
He also favours eco-taxes which he said would linked to redistribution, to give more help to the poorest in society.
He is fiercely anti-consumerist and is convinced that people are starting to realise "if we base our identity on more and more consumption it's not very good".