At the only environmental hustings planned before May 5, London’s mayoral candidates outlined major environmental changes they want to introduce if elected – from creating an energy company for London to banning HGVs in rush hour.

So who is London’s greenest mayoral candidate? That was the big question on everyone’s lips at the only environmental hustings being held before May’s election, organised on Friday by Greener London, an alliance of nine leading charities.

Sean Duggan, former group editor of our south west London titles and a committed environmentalist who launched and ran our Green Guardian project across south London for five years, reported from the hustings.

Sian Berry, the Green Party candidate arrived at the central London venue resplendent in a green blouse and a green jacket.

Caroline Pidgeon for the Lib Dems wore a deep green blouse, and even Conservative hopeful Zac Goldsmith sported a green tie for the occasion.

Only Sadiq Khan for Labour bucked the trend, sticking to his trademark white open neck shirt and grey suit.

But of course it is not how much green they wear, but how green their policies are that matters, and on that score Mr Khan - not well known for championing the environment until now - turned out to be the biggest surprise of the evening.

At the start of the meeting he told the 400-strong audience that he wanted to use “the R word”, radical – though not in the coded sense that he felt it had been used to suggest he was a “radical” Muslim in a controversial leaflet put out by Mr Goldsmith, who insists this was not his intention.

Mr Khan, currently the front-runner in the election race, said “we need a radical mayor” to drive forward the environmental agenda for London: “You have got to be ambitious, and dare I say it Zac, radical.”

The Tooting MP even agreed on Friday to the Green Party candidate’s plan to set up an energy company for London.

Asked whether he would emulate a scheme launched in Nottingham six months ago where the city council has started selling energy cheaply to residents, saving around £78 per household, he said he would – something which could help the million Londoners currently in fuel poverty.

He also backed Ms Berry’s proposal to use the company to buy up excess energy generated by Londoners from solar panels.

He was the only candidate not to support the appointment of a green infrastructure tsar for London – insisting these issues were so important that he would personally coordinate them as mayor.

He said: “My job is to mainstream these issues, so it permeates everything we do.”

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AIR POLLUTION

With 10,000 Londoner’s a year dying prematurely as a result of air pollution, much of it caused by diesel vehicles, all the candidates agreed tackling this was a top priority.

Mr Goldsmith said if the next mayor didn’t take effective action the Government would have to step in. He explained that by 2018 all new taxis would be electric and with zero emissions but many were not due to be replaced until after that date.

He said the obvious solution was to retrofit them to run on liquid petroleum gas, which would cost about £6,000 each, and he said he would find a mechanism for doing this so that drivers were not out of pocket. He pledged that all buses would at least meet the ultra low emission standard by 2025.

Ms Pidgeon said she would get Tfl to “bulk buy huge numbers of the new fully electric taxis” to get the price down and then lease them or sell them to taxi drivers to get a rapid shift to cleaner vehicles. She would also help subsidise the extra cost of the improved vehicles – around £10,000.

She said the capital should follow cities around the world and start introducing electric buses, both single and double-decker, but warned that the lack of charging infrastructure was “the elephant in the room” and a lot of work needed to be done with the electricity providers to roll this out.

Ms Berry backed the scrappage and subsidy proposals for taxis but said Tfl plans still showed 2,000 diesel buses on inner London’s streets in 2020 and “that absolutely has to change”.

She added: “Cleaner vehicles are all very well, but we do need to be reducing the amount of traffic on the roads.”

She said that many organisations recognised the need for a London-wide, distance and pollution based road charging system with the money raised to be reinvested in walking, cycling and public transport.

Mr Khan said there should be a diesel scrappage scheme, not just for taxis, but for family vehicles, lorries and vans. He said an ultra low emission zone should be rolled out more quickly and expanded not just to the north and south circular roads but also to the arterial roads coming into London.

He proposed inviting tenders for new electric or hydrogen cell buses not just for London but ones that could be used all round the world.

He said that with 300 buses an hour at peak times in Oxford Street the pollution there could be more dangerous than in the centre of Delhi – and he planned to pedestrianise the road – an idea supported by Ms Pidgeon.

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CYCLING AND WALKING

To make the streets safer for cyclists Ms Berry said she wanted other candidates to commit to expanding the existing cycle superhighways and ensuring they were segregated from other road users.

She also wanted more consultation, particularly in outer London, to identify junctions which are dangerous for bikers and roads that need safety measures. She said that the next mayor must go back to the 'hierarchy' system where they invest first in walking and cycling, then public transport, and finally other vehicles.

Mr Khan agreed with the Green Party candidate that Tfl needed to spend more money on cycling and he wanted to see more “quiet ways” and more bike stands in town centres.

He also put forward the idea of creating flyovers for cyclists at particular dangerous roads. He said: “We have got to be really ambitious about cycling – it is sustainable, healthy and really cheap to do.

Mr Khan said many walking routes around London were now blocked by private owners and he wanted to use the London Plan to help increase public access and give them “the right to roam” – though he acknowledged this would be difficult to do with existing developments.

Mr Goldsmith said the design of HGVs needed to be improved to make them safer for pedestrian and cyclists as at present “even the best HGVs are dangerous”. Mr Goldsmith said he believed that seven deaths in London last year were caused by them and he wanted them banned during rush hour to boost the confidence of cyclists – a move backed by the Lib Dem and Green candidates.

He said: “Removing the HGVs at that time of the day would have a massive, massive impact.” And he said that new shopping centres should centrally coordinate the delivery of stock to reduce the number of lorries on our roads.

Caroline Pidgeon said the cycling desk was “buried” at Tfl and overseen by bus men whose primary interest was in buses. She proposed creating a separate directorate for walking and cycling with equal clout. She said that Tfl now spends two per cent of its budget on cycling and she wanted to increase that by half by 2020. She said she wanted people to look back and say “that was the point that London became a truly cycling city.” She also wanted to see more freight moved on the Thames rather than by road.

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SOLAR ENERGY

James O’Brien of LBC radio, who chaired the discussion, highlighted the fact that London has the lowest percentage of solar power of any region in Britain. The target is to reduce CO2 emissions by 60 per cent by 2025, but London is only on track to achieve a 40 per cent reduction. He challenged the candidates to create a tenfold increase in solar energy - the equivalent of 200,000 solar rooftops.

Mr Khan said he planned to create a team in City Hall called Energy for Londoners to look at power generation and supply in the capital. He said that just 1 per cent of its energy currently came from solar power but “we can get to 20 per cent without too much difficulty”. He said the Olympic car park in Stratford had more solar panels than the whole of Tfl’s estate – which is the size of 60 Hyde Parks. He wanted to see solar panels on the railway sidings and roofs and on new buildings across the capital.

To sustained applause, he attacked the Government for cutting solar subsidies and feed in tariffs which he said had cost 20,000 jobs and said: “What we need is a mayor on the side of solar energy and the 21st century.” He said the mayor could bulk buy panels to bring down the cost and he should work to make better use of waste heat – something that is common on the continent.

Ms Pidgeon said there were 3,000 jobs in London in the solar industry and a number of companies had collapsed as a result of the Government cuts. She said she would set up a solar task force to audit all GLA buildings along with fire, police and ambulance structures and create a London feed-in tariff to double the rate of installation.

Ms Berry wanted to create an energy company for London - a proposal backed by Mr Khan - to buy excess solar energy and sell it to consumers across the capital. This would challenge the power of the big six energy companies and help reduce fuel poverty. She also wanted a massive increase in solar on Tfl infrastructure – power she would use to run Crossrail with 100 per cent green energy.

Mr Goldsmith defended the Government cuts saying that the cost of installing solar panels as coming down by the day and there was still a five per cent return on installing them. He said the price would fall by a third if the tariffs imposed by the EU on solar panels from China could be avoided.

Mr Goldsmith highlighted a scheme by the mayor of Bristol which identified space on existing rooftops where community solar panels could be sited. He said there was huge capacity for more solar power in London and he didn’t think a tenfold increase would be a big ask.

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RECYCLING

All the candidates rejected the suggestion that they should step in to create a unified recycling system across the capital. London currently has 20 separate schemes and some of the lowest recycling rates in the country. They all agreed it was best left to councils, but Mr Goldsmith said he would work towards creating a single set of standards for the capital and he believed this would drive up recycling rates. He also wanted to work with producers to reduce waste and packaging.

Ms Berry suggested centrally coordinating information about the borough schemes and raised the idea of banning single use plastic bottles in the wake of the introduction of the charge on plastic bags. Mr Khan said that the mayor could ensure there are no more incinerators and work with councils to set ambitious recycling targets and help ensure they get the best deal from contractors.

EUROPE

Asked whether staying part of the EU was good for the environment in London, all the candidates were adamant that it was, apart from Mr Goldsmith who has come out in favour of Brexit, and told the meeting “there are pros and cons, I can’t answer it really”.

GARDEN BRIDGE

Boris’s Garden Bridge project came in for sustained criticism. There was prolonged applause from the 400-strong audience for the suggestion that the public money going into it should instead go to protect the capital’s parks and green spaces threatened by local authority spending cuts.

Only Mr Goldsmith defended it, saying he would not cancel it if he became mayor and he believed people would be proud of it in the future as part of the proposed National Park City scheme. He said that the bridge was being paid for privately apart from £10m from the public, £20m in loans and £30m in waived VAT.

Responding to calls for the project to be blocked, Mr Khan said he believed the money had already been spent but he wanted to investigate the procurement process and whether correct procedures had been followed.