While there is a long way to go for the Green Party, Caroline Lucas's electoral triumph is hugely inspiring for party activists and the left as a whole.
But where do the Greens go next? Membership and activity are rising fast, but to make a real difference the stark realities of power need to be faced.
Without democratic reform it will be challenging - although not impossible - to elect more MPs. Britain has a democratic deficit and most voters rightly feel they have very little influence on politics.
Our neoliberal government will not be bringing real democracy to Britain fast. The agreed referendum on alternative voting (AV) provides very little change. AV is not a proportional system, it merely means that any candidate in a constituency must get support from 50 per cent of voters.
The idea that if a party gets 10 per cent of votes it gets 10 per cent of seats is still a long way off.
The Green Party needs to make a priority of campaigning for electoral reform, an elected upper chamber and other reforms to bring democracy to Britain.
It also needs to be putting the Earth first. Green politics is still about the environment and environmental threats should be our number one political priority. But environmental politics is pretty firmly off of the agenda at present and when politicians do talk green, action is usually in the form of ineffective market-based palliatives such as carbon trading.
The Green Party needs to prioritise real action on climate change from solidarity with indigenous people opposing mining and defending rainforests to the green new deal based on expanding renewable energy.
Capitalism is at heart environmentally unsustainable and exploitative and the Green Party is a strong advocate of practical economic alternatives based on economic democracy.
Tactically, the party will inevitably have to work with others. This is tough in Britain, where all three principal parliamentary parties have bought into the neoliberal dream.
However, Green co-operation with Ken Livingstone in London and Lucas's personal support for Salma Yaqoob in Birmingham suggest that practical co-operation with radicals in other parties is possible.
Electorally, the Green Party needs to target a small number of key parliamentary constituencies so that victories can be won in future general elections and supporting Lucas at future general elections must be the absolute priority.
The party needs to stand in as many parliamentary seats as possible. Paradoxically, only by working as a high-visibility national party will the Greens win in key areas.
We need to work hard to win at every level from parish councils to the European Parliament where it is possible to win without first past the post.
But Green politics is not just about winning elections. It is about using a variety of means to make green principles of ecological sustainability, social justice, peace and grass-roots democracy mainstream.
It is this battle for ideas that is vital. We need to be working hard in the face of a hostile media to promote two interlinked ideas. First, that we must respect the planet and not abuse ecological systems.
And second, that there is an alternative to capitalism. Finance capitalism, far from promoting freedom, threatens both prosperity and the planet.
Lucas's first speech to Parliament made the point well.
"When Keir Hardie made his maiden speech to this house, after winning the seat of West Ham South in 1892, there was an outcry.
"Because instead of frock coat and top hat, he wore a tweed suit and deerstalker. It's hard to decide which of these choices would seem more inappropriate today.
"But what Keir Hardie stood for now seems much more mainstream. Progressive taxation, votes for women, free schooling, pensions and abolition of the House of Lords.
"Though the last of these is an urgent task still before us, the rest are now seen as essential to our society. What was once radical, even revolutionary, becomes understood, accepted and even cherished."
Lucas has been putting forward a left-green agenda, helping to fight the spending cuts and in her maiden speech taking on polluting multinationals like Trafigura.
Challenged by right-wing historian David Starkey on Question Time, she was happy to defend the "socialist principles" of the Green Party.
Lucas is an impressive communicator and can put forward green ideas in an attractive and persuasive form.
Her victory shows that it is possible for the Green Party to elect members even in the difficult circumstances of British politics - and it gives the lie to those who argue that political success for radicals always means selling out.
Green-left members of the Green Party can feel pleased that not only is the party explicitly on the left but it has such a strong representative in Parliament.
Derek Wall is a former principal speaker of the Green Party.