It was an unusually humble David Cameron who spoke in Edinburgh today. He admitted that the Conservative Party "isn't currently Scotland's most influential political movement", adding that "more than a little humility" is called for when any contemporary Tory speaks in the country. And, with no little sincerity, he brushed aside those who point out that the Tories would benefit politically  if Scotland went it alone. "I'm not here to make a case on behalf of my party, its interests or its approach to office. I'm here to stand up and speak out for what I believe in," he said.
Unlike some opponents of independence, Cameron focused on the positive case for the Union, rather than the negative case against an independent Scotland. In an eloquent and emotional paean to the UK, he declared that "we have turned a group of off-shore European islands into one of the most successful countries in the world."
But it's not hard to see why his speech  will have left many Scots cold. It took some chutzpah for Cameron to claim that "we all benefit from being part of a properly-funded welfare system" when his government is imposing £18bn of welfare cuts.
In a reference to the failed Glasgow Airport terrorist attack, he boasted that the "the full resources of the UK state went into running down every lead. Our tentacles reach from the border areas of Afghanistan and Pakistan to the CIA computers at Langley." But for many Scots, this will serve only as a reminder of the disastrous foreign policy pursued by the UK government in recent years. An independent Scotland would not have gone to war with Iraq or become trapped in Afghanistan and, some will say, would have been safer as a result.
Cameron held out the possibility of further devolution after the referendum but was notably vague about the form this could take. The danger for the Unionist parties is that Scottish voters, the majority of whom support fiscal autonomy, conclude that the only way to win it is to vote for full independence. If Cameron wants to offer a truly positive alternative to secession, he should embrace "devo max".
The campaign against Scottish independence will not lead by Cameron but by social democratic heavyweights like Alistair Darling, Charles Kennedy and Ming Campbell. Today's speech was a reminder of why.