It's my party - and I'll cry if I want to.

Caroline Lucas, Britain's single Green MP, has written an open letter to Jeremy Corbyn (see The Independent, 25 August.) She calls for a
'Progressive alliance', for the next election. This alliance is to be based on Corbyn's programme, then what she describes as the unique Green contribution and, most importantly for the future, the fact that,
'The beauty of this moment, and what scares the political establishment most, is that the power of your campaign (Corbyn's campaign) is coming from thousands of grassroot voices - not a diktat from above'.

Lucas argues that
'The old politics is crumbling, not just in Britain but across our continent.' But she expresses her disappointment that Corbyn's campaign has
'Not focused more on reforming our ailing democracy. A truly progressive politics fit for the 21st century requires a voting system which trusts people to cast a ballot for the party they believe in.' And Lucas goes on to suggest that if Corbyn were to win his Labour Party leadership bid, the momentum would open the opportunity for him to spearhead the call for a Constitutional Convention
'To allow people across the country to have a say in remodelling Britain for the future.'

Exciting stuff.

The gathering of popular support for Corbyn is certainly a remarkable political fact - first brought into life by the mass demonstration called after the General Election in June - by the Peoples' Assembly. Hundreds of thousands marched in London (with a large Green contingent) showing the awakening of a new, youthful based political current, that regarded the election result, and the traditional parties and choices that it expressed, as not representing them or their hopes. Corbyn's candidacy, and Labour's new internal election rules (that Miliband thought he was borrowing from the US Democratic party) have provided another focus for this new political trend. So much is obvious, and while the concrete details of history are always unique, the new potential radicalisation was generally predicted, well before the election, by the leadership of the Peoples' Assembly - among others.

So far the new British radical movement has not been disrupted by events in Greece. But in its most political centres there is increasing interest in the progress of the left organisations across Europe that challenge austerity and a growing recognition that the great questions of the future are inextricably linked to European, not to say global solutions. But although this active layer constitutes hundreds of thousands, if not a million or two, it has yet to 'win' a leadership role in the wider British society. This fact may yet be reflected in a much closer call in Labour leadership elections than expected, if not the defeat of Jeremy Corbyn's candidacy. Should Corbyn win then the Britain's radical left has created a much greater platform to address the whole of society and to begin the task of winning the leadership of Britain's nations to a new direction.

Corbyn's 'grass roots' campaign is the opposite to Foot's campaign and his victory as Labour leader in the 1980s, where the left trade union ranks and the mass Campaign for Nuclear Disarmament were used solely as adjuncts to the decision making power of the immensely powerful trade union bureaucracy of the day. But while the political space for a new version of the Social Democrat party, presumably under the Blairites, does not exist (witness what happened to Clegg et al) a Corbyn victory would certainly herald a further disintegration of the parliamentary Labour Party. Already the negative impact of the Scottish National Party's victory in Scotland for the future governmental prospects in Westminster of the traditional Labour Party is causing serious self-searching among Labour's right wing. A Corbyn leadership would bring Labour's crisis to the fore. Quite soon new quasi-party formations would emerge inside Labour and rightist coalitions sought, to prepare against future electoral 'ruination'

The weakness of British mainstream political thought (as reflected in the media debate about Corbyn's campaign) is that it does not understand that Labour's crisis is also a feature of the crisis of the British capitalist political system as a whole. The Empire and the City of London no longer buttress Britain's political stability; they no longer allow the wholesale export of its domestic social violence and economic misery to other, poorer parts of the world. As we approach 2016 a new global economic collapse looms and the EU is in its greatest turmoil since its inception. Mass movements by the near-world's poor and war-torn are on the march towards Europe while the EU itself is in a battle royal over austerity. All of which underlines the global and European dimension of everyday political lives in the UK. And, against that background, the Tories are about to start a excoriating 'debate' in society about EU membership. It is this combination that will frame the next stage of political radicalisation, both to the left and to the right, inside British politics. It will not be a discussion about whether or not to accept Cameron's treaty compromises. It will be a social, political, economic and moral battle about what sort of society is acceptable in an advanced country, what is feasible, what would be based on human need as opposed to the defence of the wealthy; how far is this a European, even a global cause? This debate has the potential to crack wide open all three of the main traditional parties of Britain, as well as challenging the basis of our current, decrepit political system itself.

And the key for the British left in this tussle? Whether or not to join the Labour Party? Whether to set up a left inside the SNP? Build new left parties? Perhaps to federate with the Greens? All, no doubt, important tactical questions to be determined in the concrete conditions of the new reality. What is strategic here (and across Europe) is something that Britain's new left might well learn from Greece as its European interest grows; it is that the various political developments now in creation, including the possibility of a Corbyn victory, will undoubtedly require the utmost political intelligence and imagination to succeed, but most of all, the priority of continuing to build up a fighting mass movement, against austerity, for human dignity and welfare, will, in the end, be the critical precondition for any secure progress.