With the end in sight it's difficult now to remember that it was as long ago as January 8, 2012, when David Cameron used an appearance on the BBC's Andrew Marr programme on to confirm that Scots would be given a "fair, legal and decisive" vote on independence.

At that stage some ministers in the Tory-LibDem Coalition were briefing that they wanted to ensure not just a victory but a "crushing" defeat of the SNP's proposals. They argued such an outcome would 'free' Scotland from a debate that had engrossed it for years. The prize, they believed, was to settle the issue not just for "a generation" - that old cliche - but perhaps for good.

But such exuberant hopes appear to be fading, at least among some on the Coalition side. Last month one senior LibDem told me how pleased he was at a recent poll which had suggested that the final tally would be around 60/40 against independence. "We'd bite your hand off for that result," he said. But he agreed that that was not a sentiment he would have expressed two years ago.

Next week will see the beginning of the campaign proper as hostilities resume following the Commonwealth Games. The "phoney war", as Alex Salmond once described it, is over.

While both sides are nervous about the high stakes battle ahead, at Westminster there is something of a genuine sigh of relief that outside "events" appear, so far at least, not to have blown the No campaign off course.

Some ministers were privately concerned that the potential for UK intervention to tackle the rise of Isis in Iraq could bring back memories of Tony Blair and anti-war protests that would prove unhelpful as voters decide on independence. There is still time for the unexpected to have an effect.

The last Quebec independence campaign, in which a leading candidate lost a leg after being infected by a flesh eating bug, suggests nothing can be ruled out. But Downing Street is confident it is less likely there will be an error by the Coalition Government.

Stories of Coalition ministers privately suggesting they would not accept the will of the people or would perform a U-turn to agree to a currency union after a Yes vote have been seen as unhelpful. There was concern that claims in the Coalition's flagship 'Scotland Analysis' series allowed the campaign to be portrayed as too negative. And there was disappointment that a UK Government cabinet visit to Aberdeen ended with ministers portrayed as "daytrippers".

Any more 'mistakes' along these lines will be magnified in the short campaign. Although Downing Street is briefing that it expects more and more of the lead to go to Better Together and Yes Scotland over the next few weeks, there is an awareness that even greater focus will be placed on every move both governments make.

The stakes are high for Mr Cameron, which is why, while he understands the importance of allowing the Labour Party to do much of the running he has used a lot of his political capital.

A committed unionist, those close to him insist he would be genuinely upset to see Scotland become independent.

There are also personal concerns. In politics the tag of "loser" tends to stick. Mr Cameron will be hoping that until vote day, at least as the independence referendum campaign is concerned, his government makes no mistakes.