25/04/2016 08:04 BST | Updated 23/04/2017 06:12 BST

Sadiq and Zac Refused to Meet the Greens - It Could Cost Them

When I call the Greens' Mayoral candidate, Sian Berry, she's on the train to meet Britain's Chief Rabbi. It's a sign of the extremely varied - and hectic - nature of the campaign to become London's next leader. I've managed to grab ten minutes out of her packed schedule to discuss what could turn out to be a crucial moment in the campaign.

The night before we talk, the London Federation of Green Parties - the main decision-making gathering of the capital's Greens - had gathered to debate and vote on whether to back a '2nd preference' for London Mayor - a feature of the capital's Supplementary Vote system that allows a first and second choice on the ballot.

First, some context. 2nd preferences have been decisive in all of London's Mayoral elections in the past. The Green endorsement, then, can be a maker-or-breaker - handing it to Ken Livingstone when he won in 2000.

On Monday night, it was a breaker, it seems. The 50 or so Greens there unanimously voted not to endorse anyone for their second preference - to the surprise of many, they refused to back Labour's Sadiq Khan. It's the first election since 2004 that they've decided not to offer their implicit support to another candidate.

The reasons stem from the fact that this is 'a very different election' to previous ones, says Sian. "We had a long-standing working relationship with Ken [Livingstone]" - unlike Sadiq Khan. Unlike previous elections however, this time the Greens laid down four demands, calling on Khan and Goldsmith to support an end to road building, airport expansion and enforced council estate demolitions, and to reduce London's inequality.

The response from the Labour and Tory camps? "Neither of the candidates wanted to meet with us to talk about them." In fact, Berry tells me that "Sadiq specifically turned it down, Zac just didn't arrange." She mentions that Sadiq camp told the Greens he "didn't want to seek the 2nd preference recommendation." It seems like a mark of arrogance. And perhaps it's justified - he's over 10 points ahead of Goldsmith. But that's in the final round, after 2nd preferences.

When outlining why the Greens didn't back a candidate anyway - meeting or no meeting - I don't detect a hint of spite. "On the policy asks, you've got some real red lines there - Sadiq's [pro-expansion] position on Gatwick for one, and Zac has been appalling on the Silvertown Tunnel [i.e. in support]. Those are things that either of them could easily have given way on."

But there are clearly differences between Goldsmith and Khan. The latter's in support of building more council housing, promoting the London Living Wage, freezing fares and dealing with air pollution all tie in with Green asks.

Does Sian's party not risk handing Goldsmith the Mayoralty on a plate? She responds that supporters "can make up their own minds. We just didn't make a positive recommendation - there was no way we could do that." There must be differences between the two lead candidates though? Again, the answer isn't too flattering for Khan: "It's actually really hard to tell them apart. He visited the City and said he's going to be a mayor for big business - that's not what you expect from someone who says he going to be a mayor for all Londoners."

That's not the whole story, however. There was a vote on whether to support an anti-Goldsmith vote - i.e. to condemn his campaign, which some have suggested has focused on Khan's religion as a Muslim. It fell by about 4-1.

In the minority however, was Sian Berry. Yet Sian is confident, despite losing the vote, Green supporters will note the 'negative and personal' campaign that the Conservative candidate has run so far. "I hope that our party members would notice that themselves without us having to tell them."

And perhaps the whole 'recommendation' set-up will become a thing of the past. If so, it bodes badly for future - most-likely Labour - candidates. Berry is certainly no fan: "This whole idea that we should instruct our voters who to vote for anyway is a bit wrong - they can think for themselves what kind of campaigns the others are running."

It doesn't seem to have shifted how Sian is voting. I ask her if she'll be casting a 2nd preference: "I will yes, but that's between me and the ballot box."

From her vote to condemn the Goldsmith campaign, one can read between the lines. But the fact that Khan can't take for granted indirect Green support in the London Mayoral election suggests there remains a deep scepticism to Labour in the Green Party - despite the rise of Corbyn.

The Greens are treading a fine line in not treating a Khan win as a given - "whoever's Mayor we're going to have to work with them. We're going to have to talk" - particularly if they hold the balance of power on the Assembly.

Either way, Berry is confident the Greens can shake up the result on May 5th. And not just confident, ebullient: "I think we stand a very good chance of increasing our number of Assembly members [from the current two]. And with two weeks to go and a bit of momentum building, I don't see why we shouldn't win the Mayoralty as well."

Does this all mark a new era in the Greens' approach to the capital? Berry - who's radical policies and popularity make her potential party leadership contender - certainly offers something different. And though she may not make the Mayoralty, her 1st place position on the proportional London-wide list almost guarantees that she'll be a progressive thorn in the side - or ally - to whoever wins on May 5th.

Official backing or not, the Greens could yet swing it. And who knows - perhaps it will be Sian's 2nd preference that proves to be the decisive vote.

This article was first published by NovaraMedia