DAVID Cameron is a leader who has never shied from mixing the political and the personal.

He is a politician for the age of the magazine profile, a man only too willing to flash his Dualit toaster in service of the Conservative cause.

One wonders, though, if there is not sometimes too much information coming our way. To wit: that he has haircuts costing £90 a pop (more than the weekly jobseeker's allowance), and that he is too posh to be pushy in the debate about Scottish independence.

Though he has stated previously that he will not go head to head with Alex Salmond, the First Minister, in a televised debate, it was made clear this week that he is not for turning over the matter. Ever.

Hell will freeze over, Kensington will vote Labour, Craig Whyte will become a fan favourite at Rangers: all this will come to pass before Dave stands toe-to-toe with Alex with nothing but a Dimbleby between them.

The subject was raised at Prime Minister's Questions when Mr Cameron was challenged by Angus Robertson, the SNP MP. Following up a story in The Herald about Better Together plans to widen the debate outwith Scotland, Mr Robertson wondered if the Prime Minister did not fancy talking up Mr Salmond's offer of a verbal bout.

Mr Cameron replied that this was a debate between people in Scotland, and that any attempt to lure him into a TV debate was an obvious ploy to divert attention from the Yes camp's dire performance in the polls.

Just to make sure the Prime Minister would not change his mind, Labour's Ian Davidson, something of a Graeme Souness when it comes to putting the boot in, told Mr Cameron a home rule truth. No offence, said the Labour MP, but the last person that No-minded Scots want to have as their representative is "a Tory toff from the Home Counties, even one with a fine haircut". Mr Cameron rushed to agree, accepting that his appeal did not stretch to "every single part" of Scotland. We hereby declare 2014's Understatement of the Year competition closed.

It is true that Mr Cameron is about as unpopular a Tory Prime Minister in Scotland as there has ever been. Some might even rank him with Mrs Thatcher. Or Tony Blair. With just one MP to speak of, and an approval rating of 13%, he is only slightly less popular than halitosis.

So it is obvious why the SNP would wish him to go head-to-head with Mr Salmond. It is the Dumbo trap, a great big hole in the ground covered by the flimsiest of nets. It is the kind of ploy one would expect to come across in a cartoon. Why not invite the PM to launch himself off the edge of a cliff, Road Runner style? You can write the newspaper sketches now: Lord Snooty versus the Bash Em Up Street Kid; the Millionaire and the Ploughman; the dastardly English cove grinding his foot in the face of the plucky Scot. It would be Braveheart all over again, minus the posterior baring (although if Channel 5 hosts the debate, all bets are off on that score).

On the face of it there is nothing Mr Cameron would gain from taking on Mr Salmond. Which is one of the reasons why he should do it. Not the best reason, but one of them. Saying yes would be a surprise move in a so far predictable campaign. Being an apparently doomed mission, it might also earn Mr Cameron some measure of respect from Scots. Are we not famed for our sense of humour, our affection for the underdog? There is something else here, too. It does not say much for Scotland's maturity as a nation, for its ability to govern itself, if we cannot hear beyond a posh English voice and listen to the arguments regardless. A man's a man and a' that, even if he was a member of the Bullingdon.

There are better reasons for Mr Cameron to think again. It is canny strategy to characterise the independence debate as a matter for Scots only. It shows a degree of respect. It dissuades English ministers from sticking their oars in. Most importantly for Mr Cameron, it puts some distance between him and defeat if it comes to pass.

Yet to characterise the vote as nothing to do with London is disingenuous to say the least. Westminster has published paper after paper pointing out the perils of independence. Ministers have been highly vocal in their opposition, Mr Cameron included. If the arguments are strong enough to advance outside a television studio, they ought to be sturdy enough to be defended inside one.

It is ridiculous for Mr Cameron to say this is purely a debate between people in Scotland. Scotland is not debating whether to divorce Scotland. It is asking itself if it wants to carry on in a marriage with the rest of the UK.

As the highest democratically elected representative of the rUK, Mr Cameron must surely want to have his say on that directly, both to Mr Salmond and to viewers watching at home. As for the argument that it would be somehow unseemly to debate matters of state in a television studio, that ship sailed at the last General Election. The kingdom did not crumble. The worst that happened was that lots of people voted for Nick Clegg.

Mr Cameron is not agin debates, it is just that he wants to see Alistair Darling, the leader of Better Together, take on Mr Salmond. He is not alone in that. Mr Salmond seems to think that bellyaching for a debate with the PM is a substitute for going head-to-head with the former Chancellor. It is not. Any more of that and one might start to think he is as scared of Mr Darling as his supporters reckon the PM is of him.

A Salmond-Darling debate would help to inject some much-needed life into this campaign. It is disgraceful that, months to go before the vote, 34% of Scots surveyed regarded themselves as not well informed, and 9% said they were not at all informed.

Voters are worried they are not being told the score by either side, and what they do hear does not seem relevant to their lives. At this rate, large swathes of the disengaged are in danger of becoming the self-disenfranchised. Wake up to that outcome on September 19, 2014, and every one of us is a loser.

In truth, there is as much chance of Mr Cameron changing his mind on a debate as there is of seeing Nigel Farage singing karaoke with Angela Merkel. Openly changing one's mind is not the done thing in politics. Here, though, is a suggestion.

If Mr Salmond wants to debate with an opponent of prime ministerial calibre who can state the case for the Union then there is a certain MP for Kirkcaldy and Cowdenbeath who has a bit of time on his hands.

Then again, there is always the risk that Gordon Brown might regard Mr Salmond as a less than worthy opponent. But someone, somewhere needs to be the bigger person and get these leader-to-leader debates going.