The most notable aspect of the debate so far on Scottish independence is that there hasn't been one.

Alex Salmond, not only one of UK's most gifted politicians but a man who has been gearing up for an independence referendum his entire political life, has been articulating the case for Scotland leaving the Union for months. No-one, by contrast, has been putting a strong case for remaining in the Union.

Until now, that is. It is in everyone's interests, whether pro-Union or pro-independence, that there should be a strong opposition to the independence movement, in the interests of having a proper debate, and yesterday Scots finally heard the considered case for Scotland remaining part of the UK, put by the Prime Minister, David Cameron. The way he stated that case gives us a good idea of what shape the pro-Union campaign is likely to take over the next two years.

Above all it was positive, with Mr Cameron articulating not why he believes independence would be bad for Scotland but why remaining in the UK would serve Scots better. He even went so far as to state that Scotland could make its own way as an independent country but that in his view it had a brighter future as part of the UK.

Fighting fire with fire, he also invoked emotional arguments, making his speech personal and telling an audience of Scots "your heroes are our heroes", a reference to Scots servicemen and women.

The pitch and tenor of his speech showed that lessons have been learned, not only from successive Tory defeats in Scotland, but also Labour's recent woes. Labour has made the mistake in recent elections of scaremongering on independence, a strategy that turns voters off. Telling Scots they cannae manage on their own is a sure fire way to ensure a strong vote for independence and clearly that message has been received and understood.

Mr Cameron also conceded that the devo max genie is out of the bottle, though whether his promise to look at devolving further powers to Scotland will be enough to satisfy those who support a two-question referendum remains to be seen.

What all Scots need is solid information on which to base their vote and those substantive questions are now starting to come into focus. Peers and MPs are already undertaking committee inquiries into the likely effects of independence on the economy, defence and foreign policy.

What is clear, however, is that, yesterday's speech aside, Mr Cameron, and indeed George Osborne, are not the men to front up a strong defence of the Union. The Prime Minister said yesterday he hoped Alistair Darling and even Gordon Brown would get involved. Those who wish to see a proper debate take place on this question must feel the same. An English Conservative yesterday stepped into the lion's den; now it is up to those Scottish politicians of all parties that favour remaining part of the Union to unite on a shared platform and start making the case for it, so that the balanced debate Scots need and deserve can take place.