Four years ago, I stood up to speak as leader at my first Green Party Conference. I was wearing a jacket hastily purchased by a volunteer from a charity shop, a kindly (non-Green) media person having strongly advised that my green jacket didn't work against the backdrop. I learnt about using an autocue on the fly - it was the first time I'd used one, and found it was very different in the hall with an audience compared to the empty chairs of my half-hour morning rehearsal.
We had about 13,000 members. The venue was Bristol City Hall, where we had two Green Party councillors in residence. We had one press officer, about half a dozen national staff. Around the country, we had about two-thirds of the number of local parties we have now.
It was quite a contrast to two and a half years later, when I arrived at Salford for the first leaders' debate of the 2015 election, to stand beside Cameron, Miliband, Sturgeon, Farage and Wood. I was accompanied then by about half a dozen others (although a good percentage volunteers), and spoke to a national audience of millions. We had more than 60,000 members, 3,000 of whom had recently joined in one day.
Those two events are a fair measure of how far the Green Party has come. We've still got a long way to go - but we've come a long way.
British politics has also changed enormously in that time. One thing that's changed is a Labour Party that fought the 2015 election as Tory-light (with the disgraceful 'control immigration' mug among its low-lights), later saw the unpredicted rise of Jeremy Corbyn, and is now facing an uncertain future. Another is that the Liberal Democrats have disavowed both their liberalism (with their backing in the Coalition of secret courts) and their democracy (with their promise to ignore a referendum result within hours of its announcement). The Tories had the apparent consummate politician David Cameron as leader, who then made a tragic, massive mistake in making a small tactical decision to appease UKIP-leaning voters with an EU referendum. You know the rest.
After more than three decades of Thatcherism and neo-Thatcherism, we've got a voting public that's rejected the political status quo, and is searching for new answers. There's widespread anger at corporate tax-dodging, privatisation of public services is profoundly discredited, fracking is more unpopular by the day.
These changes together are the recipe for a peaceful political revolution. They're a huge opportunity, and a huge challenge, for the Green Party.
We've got a new model of politics that acknowledges we've no choice but to live within the natural limits of our one fragile planet (that's physics, really, not politics); in a democracy, you can only deliver that when everyone has a secure, decent life, without fear or worry about being able to put food on the table or a roof over their head.
This is what the future has to offer - what I'm confident will be the new common sense in our political future.
I'm not restanding after two terms and four years as leader - representing a very different political transition to what other parties are currently experiencing - but I'm not planning on going away. I'm still planning on doing full-time politics - hopefully (as befits the Green Party) at a slightly more sustainable pace.
Before I leave here, I must offer a special thank you to all of the Green Party members, councillors, volunteers and non-aligned campaigners who've helped me over the past four years. Outsiders to the Green Party frequently meet me at an event, look around behind me and ask, "Where's your entourage?"? I've never had that - but I've relied on thousands of helpers over the past four years, who've done everything from answering my mobile while I've been speaking to the media to putting me up in spare rooms, organising complex logistical details for visits in parts of the country where public transport is far from simple, and writing briefings for me on complex local issues.
It's been a wonderful four years. Thank you for your support.