I’M not sure who it was in the SNP who suggested using the Edinburgh International Climbing Arena for the party’s manifesto launch this week, but it was rich with appropriate symbolism.

Politics and mountaineering have a lot of similarities. They both require stamina, self-belief, courage and determination. The challenges are large, the rewards immense.

The venue may have been impressive, but this is a policy document very much about substance rather than style. If there’s one phrase which sums up the SNP manifesto, it’s that it is a positive alternative to austerity.

The party has put forward a considered, costed, intelligent and mature programme which will boost prosperity, reduce inequality and increase fairness right across the UK.

For families, there’s a near doubling of free childcare; promises that the money saved by not renewing Trident will go to health, education and children and lower energy bills.

There’s pension protection and a review of retirement age for older people, while businesses will be given more opportunity to grow and, vitally, to create jobs. For everyone, there’s protection for the NHS, reversal of benefit cuts and an end to austerity.

This is a programme which speaks to the heart of Scotland – but also, uniquely in the SNP’s history, to the whole of the UK too.

With its calls for support for vital public services, an attack on poverty and backing for modest increases in spending, it will resonate strongly with an audience south of the border which feels dispossessed by the continuing cuts agenda of the Westminster parties.

This is the SNP thinking big and, as Nicola Sturgeon eloquently put it at Monday’s launch, finding common cause and building alliances with others of like mind right across these islands.

There are massive numbers of people south of the Border who are, as in Scotland, appalled by what the Tories have done to the economy and public services.

They want the security of knowing a welfare safety net is there, that they will continue to receive first class healthcare free via a public NHS and that there is a real will to create jobs through economic ambition.

These people are wearied by the coalition cuts programme prosecuted by David Cameron and Nick Clegg and endorsed by Labour earlier this year in their infamous vote for another £30 billion of austerity. These English voters, too, would benefit hugely from the possibility of the SNP holding the balance of power in the House of Commons and – Nicola’s words again – keeping Labour honest.

Yes, of course this is a programme for a stronger Scotland. It anchors enhanced devolution by demanding that the proposals of the Smith Commission are delivered quickly and in full. But it is unequivocally a programme for a better, fairer UK too.

That is why, following her hugely successful TV debate performances, the popularity of our First Minister continues to rise in every corner of these islands.

This is causing near panic in other parties, with the latest intervention by John Major claiming that the SNP would hold Westminster to ransom merely being the latest example. Major completely misses the point – this is about democracy, and it’s the people who are in charge, not the politicians.

Ed Miliband and his advisers are also playing power politics. They’re trying to send the message that they won’t treat in any way with a large, power-wielding group of SNP MPs, without actually ruling it out.

They’re leaving the door open, because they have to. Labour’s candidate for London Mayor, David Lammy, has said as much.

All talk of a coalition between the two parties is a smokescreen: in my view neither side wants that. An issue-by-issue deal, focused on progressive policies, is a different matter.

There are Labour MPs in England as well as Lammy saying privately they would be happy to work with us, especially on issues such as stopping the renewal of Trident.

The different histories of Labour and the SNP, combined with the enthusiasm Miliband and Balls have for more austerity, mask the fact that the two parties actually do share some common ground.

With this in mind, I just don’t see that Miliband is going to hand the prize of Downing Street back to David Cameron. Not when a party with many social democratic views similar to his own could put him in there – and especially when returning the Tories would almost certainly cost him his own job.

No. He might sign away a replacement for Trident through gritted teeth and dumping austerity is going to be highly embarrassing for him. But that’s the way it could be and many in his own party will likely come to praise him for it.

Welcome to the world beyond manifestos. The world of realpolitik. And from May 8 on, it’s going to be very interesting.