By Emma Griffiths
BBC News political reporter
Family: Lives with partner
School: Pates grammar school, Cheltenham. Trinity College, Oxford.
Lives: Kentish Town
Career: Medical copywriter, former Green Party principal speaker
London Mayoral candidate Sian Berry says she is not intending to wage war on the city's motorists should she win the mayoral race - but then again, she doesn't intend to make life any easier for them.
Founder of a group which campaigns against using big off-road cars in towns, she says: "There's a place for 4x4s in the countryside, just not down Oxford Street."
The Greens' mayoral candidate was spurred into joining the party by the fuel protests of 2000.
Having voted Labour in 1997, she was annoyed at what she saw as a cave-in to "half a dozen blokes with lorries" - the government's decision to scrap the fuel price escalator.
Now she wants to change the British mindset about car ownership.
Her vision is of a London teeming with "car clubs" - where people essentially hire a car per journey, without the cost of buying and maintaining their own car.
She says it would mean people were less likely to use their car for short trips when they could walk or talk public transport.
"I'm not against people driving, but I do think we need to get away from this idea that you are 'a motorist' that you are in a tribe that is 'the motorist' therefore you will take all your journeys by car and everything that gets in your way is a bad thing," she said.
"We are all basically just people trying to get around."
Ms Berry also backs a 20mph speed limit in place throughout greater London, except a few major roads, to reduce accidents and "smooth out" traffic.
She also wants to see greater funding for cycling and pedestrians, 20p fare cuts on buses and off-peak Tube journeys, 24-hour free travel for pensioners and more student travel discounts.
Among her first targets as mayor would be road building programmes like widening the north circular and building the Thames Gateway bridge - she believes axing the latter could save £500m, to be pumped into more sustainable transport policies.
A greener and more affordable London
Free insulation for all homes
20p cut in bus and off-peak Tube fares
A £7.20-an-hour minimum wage for London
20mph limit across London, except some major routes
And she would ban vehicles from the West End every Sunday, and have one shuttle bus running up and down London's congested shopping heartland - Oxford Street.
Ms Berry says she understands some journeys, particularly in outer London, need a car and she says she does not aim to "demonise" die-hard "petrol heads" - she prefers trying to talk them round.
"I've been on the Nick Ferrari show, who's Mr "I've got two 4x4s" and spouts the most terrible rubbish constantly.
"But I don't get annoyed with him and I do engage with him properly and we have a decent chat most of the time and we get on reasonably well, even though we disagree violently in rational terms we are very civilised. We talk to each other and have a discussion."
'Make things happen'
Ms Berry, 33, grew up in Cheltenham but has been in London for 11 years and lives with her boyfriend in Kentish Town. The Oxford engineering graduate worked as a medical copywriter but says she got fed up writing about "lifestyle drugs".
She went on to found the Alliance Against Urban 4x4s and has enjoyed a rapid rise to the top of the Greens since joining in 2001. She was the party's joint principal speaker in 2006 - the closest thing the party has to a leader.
She says her "determination to make things happen" is what got her noticed - and would serve her well as mayor.
"I'm seen as someone who can get things done," she says.
"It's a huge job, but it's a leadership job. The day to day job is making sure London works and leading London in the right direction. I think I have got the right vision for London."
But she says she wants to show everyone that there's something in it for them if they vote Green.
Insulation for all
"Part of the problem with green issues is people think there's nothing in it for them. They think a green vote is a purely altruistic vote if they are feeling generous ... they're not going to gain from this. I'm really trying to get across how much we are all going to gain from a Green mayor."
In addition to her 20p fare cut, she has another eye-catching policy up her sleeve. She believes everyone in London should be entitled to free insulation for their homes.
Her argument is that restricting free insulation to people on certain benefits means "putting up barriers" many people feel excluded, and half of those who are entitled will not take it up.
While London's millionaires would not be top of her list , she admits they would be entitled - but she would concentrate on promoting it to the less well-off, including the one in 20 families living in "fuel poverty".
She believes she could get energy companies themselves to help pay for the policy if it could be done in a cost effective way - when home owners are moving or carrying out work anyway.
London's insulation and home energy use is "rubbish" she argues: "We use more energy heating our homes than they do in Sweden - and they have snow on the ground for half the year."
'Ken and Boris show'
She also wants to see "feed-in tariffs" - in which energy companies are obliged to buy energy from householders who generate their own electricity, for example through wind turbines.
And while she is pleased with Ken Livingstone's congestion charge and the recent announcement that the highest polluting vehicles will pay £25 a day - a policy she takes credit for - she wants to push things further.
She says Mr Livingstone cannot put real pressure on central government, because as a Labour mayor he is linked to the government.
Be it on London's climate change goals, campaigning to raise the minimum wage to £7.20 an hour, forcing developers to reserve 60% of housing developments for affordable housing and 50% of commercial developments for small businesses, she wants to push the boundaries.
Too much money is wasted "buttering up big business", she says, which could be better spent on insulation and smaller, local businesses.
"I don't want to smash the City, what I don't want is for London to rely on the City as much as it does. We rely something like 40% of our GDP on that square mile and the businesses associated with it. That's not sustainable - that's not an economy that will resist a collapse in the financial system."
She believes Mr Livingstone has allowed developers to work around the rules where they can. She would put more pressure on them to make more new builds environmentally friendly - starting with a requirement for 20% of their energy to come from renewable sources - like solar power - to be raised to 30% within a few years.
But could there really be a Green mayor in London?
"Already I think people are getting tired of the Ken and Boris show with them just shouting at each other... I think people will be very interested to hear from us as time goes on," Ms Berry said.
But she admits: "I think it would be something of an event - it would be quite a significant thing if London is to suddenly turn around and elect me as mayor.
"I have got a lot of votes they are just second choice votes at the moment."
Controversially she asked her supporters to give Ken Livingstone their second choice votes - a call reciprocated by the current mayor.
But deal or no deal, she is going to do all she can to persuade people to put her first.