You go away on holiday for a couple of weeks and what happens? A bearded lefty ends up leading Labour's UK leadership contest.

Okay, the Islington MP, Jeremy Corbyn, is only ahead in some "internal" polls viewed by the New Statesman magazine. But the man who is prepared to say he has “friends” in Hamas, wants to scrap Trident and put up taxes is already the story of the Labour leadership campaign.

As of the weekend he had secured 40 constituency party nominations against right winger Liz Kendall's five. Everyone seems to accept that Mr Corbyn has been getting his anti-austerity message across to large numbers of disillusioned Labour members.

There are rumours, too, that mischievous Trotskyites and Telegraph-reading Tories have joined the Labour Party purely to back Mr Corbyn. But you can't start going around holding inquisitions of prospective party members. If they are joining Labour as a flag of convenience it is because Mr Corbyn has been sailing ahead. He has the Big Mo.

I very much doubt if he will sail into the leadership, still less into Number 10. He has never really regarded himself as a power broker. He's essentially an outsider, an intellectual provocateur, keeper of the true socialist faith.

If only Labour had someone like Nicola Sturgeon, a social democrat with similar politics to Mr Corbyn but who is also deadly serious about power and is a brilliant communicator. It's worth remembering that, in The Herald/TNS poll after the TV debates, Ms Sturgeon emerged as the most popular leader, not just in Scotland but in the UK.

But even assuming he loses, Mr Corbyn has already won a significant victory by demonstrating that values of collective security, nuclear disarmament, wealth redistribution and social welfare are still viable in the Labour party.

The other candidates – Yvette Cooper, Andy Burnham and Liz Kendall – have been left flat footed dismissing Mr Corbyn as a “self-indulgent fantasy candidate”. Well, it's a fantasy that an awful lot of Labour members seem to share, as the Commons welfare debate demonstrated.

Perhaps Mr Corbyn has shown that Scotland is not such a special case after all. Metropolitan commentators often dismiss the SNP success as identity politics, anti-English nationalism. But as Mhairi Black made clear in her Commons maiden speech – which has been viewed more than 10 million times – that nationalism had very little to do with the SNP's recent success.

The SNP tsunami was all about politics: rejection of the Westminster consensus on low taxation, austerity, welfare cuts and nuclear defence.

Commentators in the UK and Scottish media have been alternately amused and perplexed by the Corbyn/Sturgeon phenomenon. Some think Scottish voters have “gone mad” or been seduced by evil cybernats. Now it looks as if large parts of UK Labour may have gone mad, too.

What is really going on is the disintegration of the Westminster consensus, the identikit politics of centralism; the “responsible” agenda in which welfare is unaffordable, the NHS unsustainable, higher taxation unthinkable, privatisation unchallengeable.

As in Scotland, social media has allowed voters to see radical ideas taken seriously for a change. Labour members are turning away from the established channels of political communication and talking amongst themselves; reassuring each other that change is possible.

Remember: Tony Blair was a radical once. He won in 1997 on a wave of popular demand for change. I recall (with some embarrassment) describing his Labour landslide as a “people's revolution”. The old corrupt order of Tory sleaze and Thatcherite privatisation was, we believed, being replaced by a modernised, post-industrial Labour party that, as Mr Blair himself put it, “refashioned essential Labour values for a new era”.

Unfortunately, we got something rather different: tuition fees, a moratorium on tax, market reforms in the NHS and an illegal war in Iraq.

The one area of 1990s Labour radicalism that did endure, paradoxically, was devolution. The creation of the Scottish Parliament in 1999 opened a new space in UK politics that has allowed these social democratic ideas to be revived in a new context. In a sense, Holyrood fulfilled the Blair mission statement.

Politicians of the left no longer have to rely on the mainstream media to put their message across and they can see a different politics at work in Scotland. Labour members like Mr Corbyn because he seems to believe in something.

They're fed up being told that they can't do this or can't do that because it isn't “grown up politics”. Corbyn is 66, and he thinks it is.