Gray: Clegg broke a promise worth £800m - the SNP broke one worth £2 billion

There are over 80,000 students living and studying in Edinburgh, and over 250,000 in the whole of Scotland. Theirs is a demographic likely to prove crucial in deciding the outcome of 5 May's general election - that much is, by now, received wisdom, but for Scottish Labour it's a sacred creed. The Conservatives and the Liberal Democrats are both likely to sustain heavy losses thanks to the unpopularity of their Westminster wings, and the Scottish National Party have been left vulnerable by a painful four years in government. With opinion polls suggesting a strong showing likely for Labour, party leader Iain Gray is cautiously optimistic.

In the basement of a stationery shop off Shandwick Place, Gray pushes home his point with a faintly Blair-like hand gesture. He's just launched Labour's small business manifesto to a gaggle of assorted journalists and bemused shop staff upstairs, so he's pushing the economic message today. From his perch to Gray's left, the Labour leader's silver-haired spin doctor Simon Pia keeps a careful watch on our interview.

Higher education is "absolutely crucial" to Scottish Labour's platform, he says. "If you look at economies that are growing, it's not difficult to see that the number of graduates in the workforce correlates with economic growth." He even tries to sell the business manifesto directly to students: it is, after all, partly focused on "creating a whole range of opportunities for young people."

But the real question here is whether the Scottish system of free tuition is sustainable, and on this point Gray seems hesitant. "We believe it is," he offers. "That's why we're making a promise." Surprisingly, he even finds time to commend the current administration. "You know, for a long time there was talk of a funding gap of £800 million. I said it was difficult to see how that gap could be bridged, but the Scottish Government has managed to bridge it and bring the gap down."

He doesn't argue with the SNP's estimate of a £96 million funding gap for higher education, though he largely reserves judgement. "There are uncertainties," he says, "because we don't know until July at what levels English institutions will peg their fees."

His answers on questions of higher education tend to be tentative - it's clearly an issue over which the Labour policy wonks have agonised, but they seem to have reached few solid policy conclusions. His wariness on funding issues, in particular, risks giving the impression that if brought to power, a Labour government may put the question of free tuition back on the table.

Gray's views on the subject of fees for non-Scottish students, meanwhile, bring to light another commonality between the Labour and SNP higher education platforms "It's inevitable," he tells us with a slightly unhappy note in his voice, "that fees paid by English students will go up. We can't continue with having £9,000 below the border and £1,800 here."

His candour is telling, and it's indicative of a general consensus forming around this issue. No-one expects fees in Scotland to remain at their current levels, but as social democrats Scottish Labour seem reluctant to let it get anywhere near the £9,000 level.

On EU fees, Gray once again joins the SNP in adopting a pragmatic view of things. Under EU law, European students must pay the same fees as home students. "That's EU law," he says, "but we support the Scottish government in exploring new ways of looking at this." The implication behind his faintly euphemistic turn of phrase is much the same as that hinted at by Alex Salmond in conversation with The Journal: that this is a piece of EU legislation that policymakers want to circumvent if possible. "The Scottish Government have said they're exploring ways of making them make a contribution," Gray remarks, cryptically. "But a solution isn't clear."

As we talk, the Universities and Colleges Union is about to begin its second round of industrial action in as many weeks, but Gray is nomcommital when pressed for an opinion. "There's a whole number of issues around this sector that need to be addressed," he says, tactfully.

But then Gray does something that seems distinctly out-of-character: he takes a swipe at the opposition - and he doesn't hold back. The issues he refers to "should have been sorted out years ago," he claims. "Crucially, look at the 2007 promise by the SNP to replace loans with grants to eliminate student debt: what happened to that? Indeed, this was a golden pledge by the SNP during that year's election, with no sign of it being fulfilled...

"People criticise Nick Clegg - that was a promise worth £800 million which he broke. Alex Salmond's promise to Scottish students, on the other hand, was worth £2 billion!"

It's interesting to see Gray taking a more directly adversarial stance, but it's not an attitude he seems particularly comfortable with. The former teacher has been criticised for a lack of public profile compared to his SNP counterpart - according to a recent Scotsman survey, less than 20 per cent of respondents in four cities could recognise his face - but it's a contest he has little patience for. "Look, the fact that Alex Salmond is more recognisable than me is hardly surprising, when you think that he's been the First Minister for four years, he's been in politics for 20 years, and is the leader of a party which is quite a one-man band.

"In Scotland, we don't have presidential elections. We have votes on what people want."

Gray is quietly self-effacing in his answers, and he comes across as something of a Labour traditonalist: he talks passionately about a "doorstep election", boasts of 500,000 doors knocked already and 500,000 more to be knocked before the election.

Questioned on how he's feeling about the imminent election, his wary rhetoric belies what seems like a keenly-felt desire, both in Gray and the Labour Party, not to be perceived as arrogant. "We're happy to see opinion polls showing us ahead, but we won't take anything for granted," he tells us with another jab of the hand. "We'll fight for every vote, and fight for every seat."