Over the years the SNP and the wider peace movement have built what I regard as an overwhelming case against Trident on both moral and economic grounds. Since the election in May, I - along with my colleagues in the SNP Defence Group - have been building the military case against Trident.

It has been easier than we first thought because Trident - despite being such a massive drain on the UK defence budget - is not actually a military weapon. It is a political weapon which can never and will never be used.

A huge amount of money spent on weapons of mass destruction that could be redirected to allow the UK to do good, whether peacekeeping, reacting to emergencies like the Ebola crisis or act a great deal more decisively and effectively to alleviate humanitarian crises like the one we are experiencing across Europe, is being sacrificed on a collective military and political ego-trip.

Yet 35% of the defence procurement budget - the money set aside to keep the UK's defence capabilities up to date - is instead being wasted simply to secure the UK a seat on the United Nations Security Council.

In his memoirs, former Prime Minister, Tony Blair – by no stretch of the imagination a unilateralist – wrote of Trident: “The expense is huge and the utility, non-existent in terms of military use.”

But he decided against cancelling Trident because in his words, it would be “too big a downgrading of our status as a nation.”

And I believe that everything you need to know about Trident is contained in those two sentences where Blair admits that the UK’s obsession with having an independent nuclear deterrent is little more than a former imperial power indulging a desperate search for a better yesterday.

Of course the last thing the UK’s independent nuclear deterrent is - is ‘independent’. It’s American. It’s designed, manufactured, overhauled and even tested in the United States. We know it will be an American Commander-in-Chief whose finger will be on the button, not a UK Prime Minister. And in about 18 months, the finger could be that of President Donald Trump.

We are being told constantly that the world is a far more dangerous place than at any time in the past. Perhaps that’s true. But as the threats and challenges we face change, why does our response to them stay exactly the same?

The threat to the UK isn’t from an expansionist rival nation state hell-bent on taking our land, the major threat we face come from ideological extremists and terrorism.

The threats we face are from the mass movement of people away from drought-stricken parts of world as they search for water and other natural resources. Indeed by 2045 it is projected that over 70% of the world’s population will be urban dwellers and many of the poorest will be concentrated into mega-cities in South America, Africa and Asia.

Yet the UK’s response is to spend £100 billion on a submarine based nuclear missile system. The simplest question to ask ourselves and the most difficult to answer is, in those circumstances, who will those Trident missiles be aimed at.

Soon Westminster will be asked to approve the ‘main gate‘ decision for renewal of Trident on a like-for-like basis – to be dumped on the Clyde for the next fifty years. It is an immoral obscene and redundant weapons system – the deadliest nuclear arsenal in history. The SNP will vote against it at every opportunity.