David Cameron tried to stave off the threat of Scottish independence – and the end of the United Kingdom – by promising more devolved powers to Scotland if the country votes no in the referendum about whether or not to secede.
The Prime Minister refused to specify what powers he might be willing to give to Scotland and said he would not elaborate until after the vote, expected in 2014.
But the move was an attempt to regain some of the initiative from the Scottish First Minister Alex Salmond, who has made much of the running on independence in recent weeks.
On a visit to Edinburgh yesterday to see Mr Salmond, Mr Cameron appeared to concede that his own Conservative Party was so toxic north of the border that all unionist politicians and parties would be needed to "come forward to defend the United Kingdom".
He called on former political foes such as the former Labour Prime Minister and Chancellor Gordon Brown and Alistair Darling to join the fight to retain the Union.
With Westminster's opposition to Holyrood's preference for a 2014 vote evaporating, Mr Cameron admitted that the "Conservative Party isn't currently Scotland's most influential political movement".
He added he was "ready to fight for the life of this country" and said: "I hope and wish that Scotland will vote to remain part of the United Kingdom."
Mr Cameron held face-to-face talks with Mr Salmond on his first visit north since the SNP government in Edinburgh announced last month that it would hold an independence vote in 2014. The talks were described as "constructive" by both sides, but in reality achieved very little.
The PM's strategy centred on his future promise to Scottish voters that if they voted to stay inside the UK, further devolved powers and "greater control over their own lives" would be looked at.
Despite Mr Salmond's initial diplomacy, describing the talks as a potential "new dawn", he later attacked the discussions as "threadbare".
He criticised the post-poll promise as "nothing on the table" and a rerun of an old Westminster offer to Scotland ahead of the rejected 1979 devolution vote, which he said had resulted in "18 years of Tory rule and Thatcher".
He said until further details were explained by Westminster the debate could not be advanced by "a pig in a poke". He added: "We don't know what this proposition is. So let's hear it."
Mr Cameron's strategy in Edinburgh was a highly personal one, laying great emphasis on an almost humble appeal to the Scottish electorate that a future inside the UK would keep them safer and richer. He tried to distance his government from the Thatcher years, which destroyed the Tories' political credibility in Scotland, saying he would be "deeply, deeply sad" if Scotland became independent.
Although admitting the loss of Scotland would strengthen the Conservatives' hand in Westminster, Mr Cameron told the Edinburgh audience he "wasn't interested" in just the job of running England. But he avoided any direct attempt to tell Scotland what it could and couldn't do. "I'm not saying that Scotland couldn't make it on her own, of course Scotland could, just as England could, but ideally I hope that this doesn't happen."
He said he "head, heart and soul" believed in the UK: "We are better off, we are stronger together, we're fairer together, we're richer together."
Campaigning: McCameron's Scottish roots? Just add oats
David McCameron. Oh, how the Prime Minister must wish that Scottish "son of" prefix were his to call on. On a day in Edinburgh, fighting to save the Union, he credited Sir Walter Scott, Captain Scott, and may have thrown in Ridley Scott if he'd had the time.
He said his father's father was a Cameron, his mother's mother was a Llewellyn, a name as Welsh as a leek. And he is English-born. That leaves only Ireland to embrace. This is easily achieved through his paternal grandmother, Enid, and her connection to William IV through his mistress Dorothea Jordan and the Fitzclarences. Dora's Waterford birthplace in Ireland means Mr Cameron holds all the aces.
But who inside Downing Street opted to add oats to roots for the visit north? Was a visit to a porridge factory really necessary? Kilt-making and shortbread manufacturers will now be on full alert between now and the referendum's eventual date. With only the privilege of Tony Blair's Fettes College replaced with Eton College, Mr Cameron's heritage trail looks well prepared for the fight ahead.