Today marked a notable milestone in the Scottish independence referendum campaign: the first appearance of Gordon Brown under the banner of Better Together.

The souring of Brown’s relationship with Alistair Darling during their time in Downing Street meant that Brown had until now stayed away from the cross-party campaign for a No vote headed by his former Chancellor and friend. Brown had instead opted to plough his own furrow at a series of town hall meetings as well as speaking at events for United with Labour – the Scottish Labour party’s own campaign to remain in the UK. It is a sign of the growing nervousness on all sides of the No campaign that Brown has finally been persuaded to work in tandem with Better Together.

Couching arguments in positive terms is vital for the Better Together campaign in the months ahead and Brown’s speech seems to be an acknowledgement of this.

A weekend poll by ICM for Scotland on Sunday found that with ‘Don’t Knows’ stripped out, the No lead stands at just 52-48. This is no outlier, with several other recent polls having shown the lead at 53-47 (again with Don’t Knows left out). Anyone who still harbours a belief that a vote to remain in the United Kingdom is a foregone conclusion needs to wake up, and fast.

So, what can Gordon Brown bring to the table?

Firstly, his is an unreconstructed ‘Labour’ voice. His reluctance up until now to participate in the Better Together campaign, often portrayed by the Nationalists as a Tory-funded “front” organisation, has kept Brown untouched by accusations of being “in bed” with David Cameron and George Osborne. With the SNP nakedly calling on Labour voters to vote Yes to “reclaim their party”, having a Labour figure of Gordon Brown’s stature firmly in the No camp may provide a vital bulwark against this tactic.

Secondly, Brown’s one election as Labour Leader was far more successful in Scotland than elsewhere in the UK. In 2010 Labour retained every one of their seats in Scotland and actually increased their share of the vote – in stark contrast to the party’s abysmal showing in other parts of the country. While this may have been as much a vote to keep out the Conservatives as a personal vote for Brown, it is clear that in Scotland he is not the busted flush he is often portrayed as by the Westminster-centric political media.

Third, he is a living embodiment of the notion that Scots punch above their weight within the UK. When the financial crisis struck in 2007-08 it was a Scot – nae, two Scots – occupying 10 and 11 Downing Street who were able to take the decision to bail out the banking sector in Scotland and elsewhere, whilst playing a leading role in orchestrating similar moves internationally. During the thirteen years of Labour government under Blair and Brown, Scots held all four of the Great Offices of State on at least one occasion and Brown serves as a powerful reminder to Scots that ‘Westminster rule’ need not equate to ‘Tory rule’.

Finally, there is the substance of Brown’s intervention. He has regularly sought to make pensions the centrepiece of his contributions to the referendum debate and today’s speech at Glasgow University was no different. Like many other issues, pensions have often played second fiddle in the independence debate to the rather more shrill arguments around currency, EU membership and oil and gas receipts. Yet some of the most telling interventions have been those which avoid abstract discussions about the merits of currency unions or European treaties of accession and instead focus more firmly on “the pound in your pocket”. Pensions are a prime example of this.

Brown argues that Scots benefit from being part of a UK pensions system which pools resources and shares risks across a population of 60m rather than a population of 5m. The Yes camp are quick to pounce on such arguments as scaremongering but Brown’s remarks seem carefully crafted to present this as being about the “fairness” of Scots who have paid UK national insurance getting what they deserve out of the UK system. He talks of the faster-rising working age population in the rest of the UK helping to cover the costs of Scotland’s more rapidly ageing society and says this will be “better for everyone”. Couching arguments in positive terms is vital for the Better Together campaign in the months ahead and Brown’s speech seems to be an acknowledgement of this.

Having spent the long weekend in Scotland, I was struck by the extent to which even those undecideds who are instinctively No voters do not feel they are hearing any positive reasons for remaining part of the UK.

If a No vote is to be achieved in September this absolutely must be remedied. Alistair Darling will be glad to have his old friend back in the fold. He and Brown are Better Together.