The Labour party is much more united on Trident than any coverage of the issue would suggest. Do I say that because I am an extreme optimist? No, I say it because of my experience in debating the issue with grassroots members who have been turning out on cold, dark and sometimes wet winter evenings. There is a tone in the discussions that is a far distance from Labour in the 1980s. I should know - I was there. Then, the party did not simply disagree - there was loathing, contempt or hatred. Now, trying to convince members in Tottenham to support Trident is not a walk across an open field but the conversation was collegiate, or as they would say “comradely”. Why is this?

The first point to make is so obvious that it is rarely said – everyone in the Labour party wants to see a world free of nuclear weapons. The question is how best to do that – through unilateral or multilateral disarmament. A pragmatic choice, in effect, the focus being – to coin a phrase – that what matters is what works. Of course, there are those who for whom unilateralism is a principle. That is an honourable position, and one that has long history in the Labour party going back to deep roots in the dissenting tradition of Methodism. Pacificism has never been a majority position for Labour but nor, rightly, has it ever been absent.

Commitment to disarmament leads to an ability across the membership to celebrate the success of the Non-Proliferation Treaty. The estimate in the 1960s was that there would be 30-40 nuclear powers by today, and Mohamed ElBaradei, former director-general of the International Atomic Energy Agency estimates that about that number have the capacity to be so today. But they do not choose to do so. There are only nine nuclear powers – the five permanent members of the United Nations Security Council, plus India, Pakistan, North Korea and likely Israel.

More countries than that have given them up – Brazil, South Africa, Argentina, Taiwan, Libya, Sweden, Algeria, Kazakhstan, Ukraine, Belarus and now Iran. That success for a combination of treaties, international co-operation and muscular diplomacy is accepted as multilateralism working. And more, Tony Blair’s achievement in building down the UK’s own nuclear arsenal is acknowledged.

Second, there is a consensus that the argument is not about either jobs or costs. Obviously, since the parliamentary vote is about building and maintaining the next generation of submarines, high-skilled, well paid engineering and manufacturing jobs are at stake. The unions representing those workers have a role to play in making that case and it is fair to say that there is no convincing evidence that any defence diversification could work to replace them. The point, though, is that the discussion of Trident is a serious one and the question is ultimately: is it right or wrong to have nuclear weapons? If it is right then the costs should be borne - though they are actually not onerous over the lifetime of the boats - and the jobs are a bonus. If it is wrong then it doesn’t matter if Trident is cheap as chips – we shouldn’t renew it, no matter how many jobs are created.

So, the debate comes round and round to deterrence and the diabolical logic of mutually assured destruction. This is the third point. The destructive potential of nuclear weapons is almost inconceivable - which leads to almost everyone, including myself, being in equal parts terrified and appalled by their very existence. If this were a decision for the United Kingdom and the United Kingdom alone, I have no doubt that Labour would come to a quick and unanimous decision not to have them. But we live in a world in which others have them or have at times sought them.

This question of a progressive party’s vision of Britain in the world and, in particular, how we can be a force for good in that world, is one that rightly exercises Labour. By and large that is the exam question with which party members are wrestling – and doing so intelligently. That is not to say that there is always nuance and understanding on both sides. Debate does drive out subtlety at times – if only for the sake of rhetoric or emphasis. But there is a conversation – and it is one that respects the fundamental rule that conversation isn’t simply waiting for your turn to speak. There is a lot of listening going on.

What is the emblem of this? For me it is something with a link back to the bitter debates of the 80s. One of the members who spoke in Tottenham was Martha Osamor. She was famously vetoed by Neil Kinnock as a candidate for the Vauxhall byelection in 1989. She said one thing with which I wholeheartedly agree – Labour cannot be seen to be obsessed with defence at the expense of the domestic agenda that concerns most voters. The best way to ensure that is to have a comradely debate and not tear the party apart. So far, in my experience, so good.