Shortly after Jeremy Corbyn’s election as Labour leader in 2015, Nigel Farage – the then-leader of UKIP – remarked that “the Labour party have now elected a vegetarian teetotaller who rides a bicycle, has got a beard and comes from north London. I think the Green party are in real trouble now”.

Farage was possibly right. In the run up to the general election of 2015, growing support for the Green party lead to the “Green surge”, with their polling trebling from around 2-3% to 7-8% in 12 months, and party membership jumping from 30,000 to 44,000. Some polls even put them into double digit figures of 10-11%. Amongst 18-24 year-olds, 25% were intending to vote Green. The party was seen as more radical and left-wing than Ed Miliband’s Labour, as he tried to appeal to potential Conservative and UKIP voters on the right, as well as those leaning towards the Liberal Democrats and Greens on the left. In the May 2015 election, the Green vote quadrupled to over a million (3.8% of the total vote share), for the first time in the party’s history.

Acknowledging the threat, Miliband appointed Sadiq Khan to head the Green ‘attack’ strategy. Brighton Pavilion was high on Labour’s target list, and held by the only Green MP, its popular former leader Caroline Lucas. However, Labour’s vote fell, while Lucas was re-elected with an even bigger majority. Elsewhere, the Greens did not pick up any new seats, but came a distant second in such Labour redoubts as Liverpool Riverside, Manchester Gorton and Sheffield Central, and a more marginal runner-up in Bristol West, a Labour gain. More frustratingly, in eleven of Labour’s target seats, the Green vote was higher than the majority Labour had lost by. Labour’s Chris Williamson lost Derby North to the Conservatives by 41 votes, whilst the Greens received 1,618 votes, prompting a swipe at them from Williamson. With Natalie Bennett’s Greens positioned well to the left of Labour, their votes could also have prevented Miliband from winning in Plymouth Sutton and Devonport, Brighton Kemptown, Leeds North West, Croydon Central, Bedford, Morley and Outwood, Weaver Vale, Gower, Bury North and Telford.

In June 2017’s snap election, Corbyn’s Labour gained nine of those eleven seats: Telford and Morley and Outwood were both Conservative holds, even with the Greens standing aside in the latter. Now lead jointly by Caroline Lucas and Jonathan Bartley, the Greens had targeted Bristol West, but came third as Labour turned a 5,673 majority into 37,336.

While Labour unexpectedly achieved their biggest polling increase since 1945, the Green vote more than halved, suggesting that Corbyn’s left-wing manifesto appealed to the young progressives who had previously backed the Greens. Indeed, Corbyn’s communications chief, James Schneider, admitted to voting Green in 2015. If Theresa May has virtually eliminated the UKIP threat from the right, has Corbyn done the same with the Greens on the left? An anti-austerity programme of a £10 living wage, scrapping tuition fees, renationalisation of the railways, and a rent cap: all Green manifesto pledges from 2015 which were part of Labour’s 2017 commitments.

There are, however, now seven seats which Labour could have won last year with the votes received by the Greens: Glasgow North, Edinburgh North and Leith, Chipping Barnet, Telford (again), Norwich North, Southampton Itchen and Calder Valley, the latter encompassing the trendy Yorkshire town of Hebden Bridge, known for its embrace of alternative lifestyles.

Whilst Labour cannot compete with the Scottish Green Party’s support for an independent Scotland, Corbyn and his team can still learn from the “Green Guarantee” on offer in 2017: a universal basic income, proportional representation at elections, replacing the House of Lords, access to green space for all – and a referendum on the final Brexit deal?

Theo Morgan is a Young Fabian member