MORALITY and politics are a volatile mix.

The debate on Trident renewal has been quietly waiting in the wings of British politics and is now being thrust centre stage, helped on its way by the appearance on Scottish soil of Chancellor, and would-be Prime Minister, George Osborne.

The old unilateralist versus multilateralist arguments will be reheated. John Swinney accused his London counterpart of making the “wrong moral choice” by putting weapons of mass destruction ahead of caring for the vulnerable and of properly protecting the country with adequate conventional forces.

For his part, the head of the Treasury argued the unilateralists of the SNP were, in such an uncertain world, jeopardising the safety of Britain. Who, he argued, could say what the threat to the country would be in 2060 when the new Successor sub fleet was due to come on stream?

During last year’s independence referendum Labour’s Jim Murphy, an avowed multilateralist, declared from atop his Irn Bru crate that unilateralism was what afflicted Labour in the 1980s, branding it a “flirtation with surrealism”.

But, of course, his party could just be about to vote for the dream/nightmare scenario that places the Labour crown on the head of CND veteran Jeremy Corbyn.

While hitherto the band of Labour unilateralists has been small, a new UK Parliament might bring forth what Mr Osborne dubbed an “unholy alliance” between an enlarged SNP group and an emboldened anti-Trident faction within Labour.

Ian Murray, the Shadow Scottish Secretary, and Scottish Labour’s solitary representative on the green benches, has made clear he will not under any circumstances vote for the renewal of the nuclear deterrent.

The multilateralist Kezia Dugdale, bravely, raised the prospect that Trident renewal could be debated at the autumn Scottish Labour conference. Mr Corbyn has already booked his place; win or lose the leadership.

It was shockingly suggested Mr Osborne had raised the stakes on Trident simply to add to Labour’s woes and, equally shockingly, it is believed SNP chief Angus Robertson, considering what to hold next week’s SNP Commons debate on, might opt for...Trident renewal.

In the circumstances, who could blame him?