The election of Ed Miliband as Labour’s new leader today is a defeat for Tony Blair, Peter Mandelson, the ‘New Labour’ establishment, right-wing commentators, and big business donors who funded David Miliband’s campaign.

It is a defeat for the idea that the most right-wing candidate has to become leader because they are the most ‘electable’, that appealing to a mythical ‘Middle England’ of ‘centre ground’ voters must triumph over all. This has been the dominant idea inside the Labour Party for at least 16 years, i.e. since the election of Blair to the leadership.

It is a defeat, of course, for David Miliband himself: the continuity candidate, the Blairite candidate, whose victory would have symbolised a willingness to simply carry on as before, to pursue ‘business as usual’ in the footsteps of Blair and Brown, the twin architects of New Labour and the capitulation to neoliberalism.

David Miliband was unapolegetic about war in Iraq – whereas Ed at least made some cautious anti-war noises, if rather belatedly – and is tainted by association with the last government’s culpability in torture and rendition as part of the US-led ‘war on terror’.

So it is welcome news that David Miliband was defeated. But it would be wise to retain a sense of perspective about the significance of Ed Miliband’s victory – he is only marginally to the left of his older brother, and was also part of the previous government.

On a few specific issues, especially economic, Ed Miliband has articulated policies that are more progressive than those of his brother and the last government. These reflect genuine differences, at least of emphasis, in the upper echelons of the Labour Party.

However, the representations of him as left-wing – by mischief-making right wing newspapers – are wide of the mark. I suspect many Labour leftwingers will be hopeful about this result marking a major change in their party’s direction, but there is little substantial evidence to support such hopes.

Leftwinger Diane Abbott’s poor result – around 7% of first preferences – and the inability of John McDonnell (who is to Abbott’s left) to get on the ballot indicate the continuing marginalisation of the left inside the Labour Party. The leadership contest was dominated by four candidates resolutely on the right of the Labour Party, rarely straying beyond an extremely narrow strip of political territory.

Ed Miliband couldn’t have won without the 2nd preference votes from Labour-affiliated trade unionists. The right-wing press, who loathe the Labour-union link, will become rather hysterical over the next few days, and seek to use this as a stick to beat the new leader in the longer term. But it is entirely legitimate and democratic for hundreds of thousands of ordinary trade unionists to have a say in electing the Labour Party’s leader.

The majority of union leaders will enthusiastically welcome the result, including Unison’s Dave Prentis and Unite’s Tony Woodley and Derek Simpson (and their likely successor Len McCluskey). Grassroots trade unionists should, however, be wary of investing faith in Ed Miliband to lead the opposition to cuts. He has studiously avoided anything other than very moderate opposition, and has refused to support potential trade union action against cuts.

The main battles ahead will be outside the Labour Party, though most will involve Labour members and the wider layers of supporters who look to the party for a a degree of shelter against the Tory storm. And there’s only any chance of Labour turning to the left – in anything more than a superficial way – if there’s enormous pressure from a mass movement, one which can see further than the limited horizons of Ed Miliband’s worldview.