By Ollie Stone-Lee
BBC News Online political staff
The Green Party turns 30 having played a huge role in changing attitudes to environmental issues, says one of its leading spokesmen.
Darren Johnson says the Greens can have their first MP within a decade
Darren Johnson is among Green delegates gathering in Lancaster on Thursday for an annual conference which will have an anniversary feel.
Mr Johnson, the party's candidate for next year's London mayoral elections, will use his opening speech to highlight Green success at the ballot box earlier this year.
In an interview with BBC News Online, he says he believes there will be a Green MP at Westminster within the next decade.
He points to the party's win of 11% of the vote in London last year, as well as its seven members of the Scottish Parliament.
But the record numbers of Green councillors - there are now 53 - showed the party could also prosper in the first-past-the-post polls, he argued.
The Greens started life as the People Party in 1973 and changed to the Ecology Party two years later.
They adopted their current name after watching the 1980s success of other Green parties in other parts of Europe.
Mr Johnson is upbeat about the party's achievements since its birth, citing its "huge role" in making the green agenda part of mainstream political debate.
"Green pressure groups do an important job, but the best way to get politicians to really sit up and take note is actually to stand against them and take votes off them," he says.
1973: People's Party formed, became Ecology Party in 1975 and the Greens in 1980s
1989: wins 2.3m votes and 14.9% of the vote at European elections
1999: Gets first place in UK Parliament when Lord Beaumont of Whitley defects from the Liberal Democrats
1999: Wins first elected seats in European Parliament and new Scottish Parliament
2003 standing: 53 council seats, two MEPs, three members of the Greater London Assembly, seven MSPs
The Greens were an "instrumental" force behind legislation like the Road Traffic Reduction Act and the Home Energy Conservation Act in the 1990s, he says.
And green councillors have been able to push through smaller-scale measures on a local level.
Mr Johnson joined the Greens in the mid-1980s, when the party was enjoying a big boost in its membership.
He thinks attitudes to the environmentalist agenda has changed over that period.
"If you asked people in the 1980s to talk about the green agenda, they would probably talk about endangered species, rainforests and so on," he says.
Now they might still mention such global concerns but also acknowledge issues closer to home, such as the effect of pollution on their children's asthma, he argues.
Voters now see green issues closer to home, says Darren Johnson
"People are seeing it now as relevant to them and relevant to their quality of life and that means there are far more opportunities for us."
The Greens' greatest success in vote numbers at the polls came in 1989, when it defied opinion poll predictions to win 2.3m votes and 14.9% of the vote at the European elections, although won no seats.
So is the party worried that was a high water mark in its support?
Mr Johnson says 1989 was fun at the time, but was a long time ago and the party will soon surpass the success seen that year. And he points to the fact that now, unlike then, the party has seats almost across the board.
"Within the next decade I think we will be seeing an MP in Westminster," he continues.
Measures being discussed at the conference as part of that quest include the idea of an air traffic congestion charge and plans for a national railcard to encourage people out of their cards.
New measures to promote sustainable energy are also on the agenda.
And Mr Johnson says a voting paper on improving pensions shows how the Greens are addressing a social agenda too.
"Whilst we have always had some sound social policies, I think that with more and more disaffected Labour members looking towards the Greens, we are paying real attention to our social policy," he adds.
Though not on the formal agenda, there will be more debate on the conference fringe about the idea of the party electing a leader for the first time.
Mr Johnson himself is stepping aside as one of the principal spokesmen to pursue his mayoral ambitions.