Jeremy Corbyn at the final rally of his campaign for the Labour leadership. Photograph: Sean Smith for the Guardian

Corbyn’s election represents a decisive rejection of Blairism, a vote against austerity and against war, and a vote for peace and justice. The possibilities opened up now are immense

Jeremy Corbyn has sensationally won the Labour leadership election by a landslide, taking 59.5% of the vote.

His election represents a decisive rejection of everything Tony Blair and New Labour stood for. It is a vote against austerity and against war, and a vote for peace and justice.

Thousands attended Jeremy’s meeting across the country. Tens of thousands volunteered to campaign. Hundreds of thousands voted.

We are part of a movement now rising, right across Europe, against an elite that has assumed its own power and privileges can never be challenged.

Those days are coming to an end.

But the fight ahead will be the toughest in decades. The old order will not simply roll over – not in the Labour Party, not in the media, not in our own elite.

The sheer scale of Jeremy’s victory will stay the hand of those Blairite plotters who were seeking to depose as soon as possible. But the drip-drip-drip of poisonous press briefings will continue.

The pressure will be on Jeremy to concede, handing key Shadow Cabinet positions to Blairites in the interest of party unity. They have no real support – Liz Kendall, their preferred candidate, won just 4.5% of the vote. But they have the backing of the press and powerful friends in the ruling class.

And they will hammer him over the foreign policy issues that the British Establishment view as absolutely central. A disastrous extension of bombing in Syria is currently being floated.

Jeremy is chair of the Stop the War Coalition. But Blairite diehards in his party have already claimed they are prepared to vote with the Tories to support British military intervention.

To pressure applied from above, we must supply our own, from below. That means sustaining the movements against austerity and war that we have seen coming together over the last few years.

The energy and enthusiasm of Jeremy’s campaign cannot be allowed to dissipate, either through too many concessions to the Blairite old guard, or through interminable internal disputes.

The People’s Assembly demonstrations outside the Conservative Party conference in Manchester are the first step. Arrogantly, the Tories have taken their jamboree to the city where the working class movement was born. We must take the fight to them, demanding an end to austerity.

The possibilities opened up now are immense.

All roads lead to Manchester on October 4th.