Seventy-two years ago two American B-29 bombers flew over Japan on the most devastating military missions of all time. The bombs they dropped - known as 'Little Boy' and 'Fat Man'- didn't just slaughter over 135,000 people, they changed the course of human history. Almost everything and everyone near the bomb blasts were destroyed immediately - buildings and people ripped apart as if they were made of paper. Those who survived did so with lasting scars that should have served as a horrifying reminder to all of us of the moral repugnancy of using weapons of mass destruction.
In New York this week, the United Nations is on the brink of finally honouring the victims of Hiroshima and Nagasaki - by signing a treaty to ban nuclear weapons. After scores of meetings, in Oslo, Mexico, Vienna and, finally, at the UN Headquarters - this ground-breaking treaty is set to finally be adopted by the UN tomorrow.
Despite Britain and other nuclear nations shamefully failing to turn up to the talks - the significance of this treaty cannot be overstated. I was at the talks last month, and saw for myself the power of countries working together on this most crucial issue.
A nuclear weapons ban follows in the footsteps of similar, and successful initiatives.
Chemical and biological weapons, cluster munitions, and landmines were all banned before full-scale decommissioning and disarmament began. History has taught us that stigmatising the weapons themselves, rather than the obvious hypocrisy of nuclear states lecturing non-nuclear nations, is the most effective way to prevent their proliferation.
The core obligations under Article I of the treaty prohibit states from using, deploying, developing, possessing and threatening to use nuclear weapons, under any circumstances. It also makes it illegal to assist, encourage or induce, in any way, anyone to engage in any activity prohibited to a state party under this treaty, extending the prohibitions to non-state actors as well.
Crucially the treaty also lays out the basic principles and pathways for how states that currently possess nuclear weapons can join this treaty. It recognises that conditions are not yet ripe to establish a time-bound programme immediately, but sets a clear trajectory for a world without nuclear weapons.
This treaty alone won't rid our world of nuclear weapons- no legal text can do that. But it is a very important step towards nuclear disarmament, and will have far-reaching implications for UK nuclear policy and the replacement of Trident.
By pushing ahead with building a new fleet of SSBNs (the nuclear armed Submarines) the British Government will now be directly contravening a UN ban - and risk our standing in the world in the process. This is despite the Prime Minister herself saying last year that she "will continue to press for key steps towards multilateral disarmament".
History will not judge kindly a Government of any political persuasion who chooses to spend billions of pounds on an illegal nuclear arsenal, especially at a time when our public sector workers suffer crippling pay restraint and our local services are severely cut back.
When the UN banned chemical and biological weapons Britain stopped developing them and begin verifying their disarmament - now we can do the same with nukes.
It's worth noting that some nuclear weapon states have softened their opposition to the idea of a ban: China, India, and Pakistan all abstained from the vote last winter. The stand off between the USA and North Korea shows that the possession of these weapons does nothing to reduce tensions, and instead put the entire world at risk if they are used.
Imagine what it would mean for Britain's standing in the world if we became the first nuclear weapons state to sign this treaty, and commit to ridding this country of these monstrous weapons of mass destruction.
To stop Trident replacement and plough the resources elsewhere is an act of political bravery because it means breaking from this country's imperial past and our history of imposing ourselves on others using our weaponry as a bargaining chip. But Britain is a modern country, without the need to be bound by our history, and we have a real chance to be leading the world at this most pivotal moment.
My message to both the Government and the Labour Party is clear: commit to this UN Nuclear Weapons Treaty, and do it now. To ban these weapons would both honour the victims of the past and offer the best possible protection from them for future generations.Suggest a correction