Speaking as the leader of the Better Together campaign, Darling was cheered and thanked profusely by around 200 delegates after defending the Union at a packed meeting on the fringe of the Tory conference in Stirling.

Asked by an audience member if his clipped 10-minute case for staying in the UK on economic, diplomatic and cultural grounds had been recorded for posterity, Darling joked uncomfortably that it probably had because it looked “particularly bad” for him.

With the BBC filming the occasion, Darling said: “My experience is that these things don’t tend to stay in the archives unless they’re particularly bad. A standing ovation from the Conservative Party, I’m afraid, will find its way in. Just watch the news tonight.”

Like most of Darling’s comments, the joke was greeted by laughter and warm applause.

Launching the Forces Together group for military families wanting a No vote next year, Darling said the Union meant jobs, a single market with England, a strong voice in Europe, a shared energy market, a combined armed forces, and deep cultural and emotional ties.

He said that with the SNP only needing 50% plus one to change Scotland forever, he wanted Tories to fight for every vote, and defended Better Together’s tactic of constantly questioning Alex Salmond’s assertions.

He said: “When you ask them questions they say you’re being negative or scaremongering. The definition of scaremongering is asking Alex Salmond a question he doesn’t know how to answer.”

He also rubbished the First Minister’s idea that an independent Scotland could set corporation tax rate 3p lower than the UK’s.

Darling said that clashed with Salmond’s other plan for an independent Scotland to have a currency union with sterling.

He said: “If you’re in a currency union, there’s no way that one side is going to let the other side undercut it on tax. Why on earth would you want to do that?”

Annabel Goldie, the former Tory leader, thanked Darling for his “lucid, eloquent and very, very clear case” for the Union.

Ahead of the event, around 400 demonstrators against the Coalition’s so-called bedroom tax – more than twice the number of delegates – held a protest outside the conference at Stirling’s Albert Halls.

Banners dubbed Darling “The Abominable No Man”, while a seven-foot inflatable rat bore the message: “Standing up to Tory ratbags”.

Organiser Iain MacDonald of the Unite union said: “I’m quite shocked that Alistair Darling is in there. I don’t know if it will be reciprocated with David Cameron coming to the Labour conference – I hope not.”

Meanwhile, after a fortnight of internal carping about her performance, Ruth Davidson delivered a solid enough speech to quell her critics. The Tory leader set out plans to improve failing schools by offering parents an “opportunity voucher” worth the equivalent of their child’s education. The voucher could be used to transfer a child to a better-performing school.

“It would send the clearest possible message to underperforming schools – improve the education you provide or parents will vote with their feet and choose something better for their children.”

There was no explanation of how popular schools could accommodate extra pupils.

She also said that, if in power, her party would spend £50 millon a year giving Scotland’s 110,000 full-time carers a week’s respite.

Despite unhappiness from some members over her recent U-turn on more powers for Holyrood – although a Stirling resident, one of her most vocal critics, Lord Forsyth, stayed away from the conference – Davidson said the party had to evolve, and a No vote in 2014 “won’t be a vote for no change”.

She said people wanted a more accountable parliament, and announced that CBI Scotland chair Nosheena Mobarik and former Dean of the Faculty of Advocates, Roy Martin QC, had joined her Constitutional Commission on more powers. Their work would “not only help chart a new course for our party, but for our country”, she said.

She dubbed Alex Salmond a Scottish “Del Boy”.

Davidson said the SNP offered a vision of a Scotland “where no hard choices would need to be made. Where so-called ‘free’ benefits for all would exist without question, or even debate. Where we would simply ride the rapids of supposedly neverending oil revenues. Where they promise you double the sunshine and half the rain. It’s the Del Boy model of government, where if you ask no questions you’ll be told no lies”.

But the biggest cheer came when she said she wanted to slash tax.

“The tax powers of the Scottish Parliament – those it has now and those it will gain in the future – must be used only one way – to drive down the tax burden in Scotland,” she said.

SNP convener Derek Mackay MSP said: “While Labour members look on in horror as their former chancellor becomes Darling of the Tory Conference, the people of Scotland will be horrified at Tory plans to break up our education system.

“Education for all is one of Scotland’s greatest values and one the SNP will protect.”

                                                   The Herald Scotland