Within minutes of Jeremy Corbyn’s election as Labour leader, Natalie Bennett tweeted her congratulations, asserting that the result showed rising opposition to austerity, privatisation, and renewing Trident in British politics.

It is a claim Bennett repeats when we meet in King’s Cross St Pancras Station three days after Corbyn’s election. “What it shows is that politics is shifting in our direction,” Bennett tells me. “It’s a good thing for British politics as it means there’s a broader range of views - we haven’t got Tory and Tory-lite on offer, we have a broader range of views that more closely reflect the views of the British public.

“Future historians may well look back and say this was the start of the end of neo-liberal, neo-Thatcherite Britain. The kind of terms that political debate's been conducted on over the past three or four decades are shifting, partly because that model has very clearly failed.”

Bennett’s optimism is hard to reconcile with the general election result in May. Not only did the Conservatives win a majority, but the combined Tory-Ukip vote was 4.5 million more than the combined Labour-Green vote. Yet Bennett advances the view that Labour would have done better had they been seen as more left wing. “What most people thought was the alternative was a Tory-lite labour party that was often barely distinguishable from the Tories and they utterly failed to convince voters that they were a viable alternative.”

Hence her belief that the 2015 general election marked “the last of the old dispensation, the last of the old times.” With Labour’s election of Corbyn (and even the Lib Dems nudging to the left under Tim Farron), now Bennett believes that “The Tory party is going to end up very isolated, very stranded,” and “is going to end up further and further away from British public opinion” in the coming months. She also believes that a government “elected by 24 per cent of eligible voters is clearly an untenable situation,” though exactly what incentive there is for the Conservatives to sign up to electoral reform is not clear.

If Labour have moved closer to the Green Party’s ideological position, as Bennett accepts, this could make it harder for the Greens to carve out a distinct identity on the left of the British politics. Bennett’s response to being asked about the policy differences she envisages between a Corbyn-led Labour Party and her party is unconvincing. “I don’t know.” Unprompted, Bennett then cites “rural sustainable drainage” as an example of what local Greens are doing in Gloucester. This rather bizarre response highlights the need for the Greens to articulate clearly what they offer voters that Corbyn’s Labour do not. Bennett later cites the Green Party’s close work with grassroots campaign groups and the role of members in determining policy as making it distinctive.

After the general election, Caroline Lucas, the Green Party’s solitary MP, told the New Statesman that the result showed the need “to avoid fragmenting the vote between progressive candidates,” suggesting that parties could agree not to stand in certain seats and keep the left-wing vote more united. Bennett says she is open to the idea. “Caroline made it very clear that she was talking in personal terms. Four and a half years is an absolute age in politics, particularly given how fast politics is changing now. It’s something that the Green Party will be looking at as a party as that time approaches, but that will be a party decision.”

Whether Bennett is in a position to influence the Green Party’s approach to the 2020 general election is unclear. The Green Party leader is elected on two-year terms, with the next contest next year. All Bennett says is that she will “be making a decision at the appropriate time. Politics is changing so fast we'll see.”

Many were unimpressed with Bennett’s performance during the general election campaign. Bennett herself described one interview she gave with LBC as “absolutely excruciating” after she was unable to explain how the Greens would provide 500,000 more social rent homes in the UK; several other broadcast appearances were almost as ignominious. Bennett admits that the scrutiny on her and the party “was very difficult”, citing that the Greens had “a fraction of the financial and staff resources of the other parties.”

Bennett also criticises the role of the press during the campaign. “We do have a very right-wing media - right-wing media outlets that are still all too often climate change denying, or certainly denying the need to take action on climate change, are not going to look kindly at the Green Party and they're going to be looking for any attack lines they can find.”

If Bennett feels a little ostracised by the press, the feeling does not detract from her underlying optimism. She describes the general election as “absolutely transformative” for the Greens, who gained 900,000 extra voters even if they did not win any new seats. Bennett also notes that it is 18 months since the Green Party outline a strategy to gain 20,000 members within five years; today the party has over 65,000.

As she heads to Teeside for a trip designed to build on these gains, Bennett retains her belief that the Green Party’s breakthrough, as part of a broader move to the left, is forthcoming. The revolution is always imminent. “It’s very clear that we can see massive shifts in British politics in the coming years. That movement is really exciting.”