I have rejoined the Labour party. The reasons are probably obvious, but no less exciting for someone who has been involved in the labour movement all my adult life. Jeremy Corbyn's election as leader has fired the imagination of people new to politics as well as those jaded by it, giving hope to many who had all but given up.
For too long UK politics had been constrained by the dead weight of the consensus between the main parties that cuts are inevitable. Under Jeremy, Labour is showing how neither this nor bullying xenophobia are inevitable responses to the political and economic challenges we face.
In a genuine break from the past, Jeremy is working to transform Labour and the party is beginning to expose the utterly bankrupt idea at the heart of the Tory project that austerity is the cure of its own disease.
He has taken a principled stand against the renewal of the UK's weapons of mass destruction capability that, at a cost of tens of billions of pounds, enables us to kill millions of innocent people and cause untold environmental catastrophe. I was pleased to be able to speak alongside him at a major anti-Trident demonstration in London on Saturday.
Jeremy is the first Labour leader in a generation who unequivocally supports the unions and his opposition to the trade union bill has been crucial. In his first major speech as leader, Jeremy told the TUC conference he fully backed the PCS strike against privatisation at the National Gallery that was nearing its 100th day. This shift from having a leader shuffling in embarrassment over industrial action or, worse, condemning it, was desperately needed.
On too many issues Labour aped the Tories for too long. It set itself apart from people like me - afraid to call itself socialist, even as the inequalities and injustices inherent in capitalism were plain for all to see. I never again want to watch as Labour MPs cheer a Labour prime minister announcing that tens of thousands of civil servants will lose their jobs, while public services are being privatised, lining wealthy shareholders' pockets.
So yes I have been a severe critic of Labour in the past and I was denied a vote in the leadership election because of it. I did say if you judged a government by how it treated its staff, New Labour was the worst civil servants had known. Does that mean I wanted a Tory government? Of course not. I said at the time I had no illusions David Cameron would be better and I have said since that his coalition government was indeed worse.
We have already seen how the corporate media barons - desperate to maintain the status quo - have reacted to Jeremy's success, and this will only intensify. Their response is essentially defeatist, so it is our job to change the political landscape to make it impossible for this to prevail. Jeremy does not just need the support of a couple of hundred Labour MPs, but the kind of social movement he has talked about since first declaring his leadership bid.
Like Jeremy, I want a society where people do not just worry about climate change or the soaring use of foodbanks, or whether Google pays its tax while children go hungry, we want to do something about these things. Jeremy knows this cannot be achieved without winning elections. But it will also require people in our communities and our workplaces campaigning to keep these issues at the top of the political agenda.
I have joined to support Jeremy in transforming the party. And I want as many people as possible to join Labour, and to get involved in the fight against cuts where they live. This is our chance to build a social movement and form a government that can offer hope to the millions of people that deserve so much better than these contemptible Tories.
Follow Mark Serwotka on Twitter: www.twitter.com/pcs_union