The election of Zack Polanski to the leadership of the Green Party of England and Wales caused a political earthquake. While Labour haemorrhages support, the far-right rises and a new anti-capitalist party struggles to be born, Polanski has seized the initiative, resulting in record-breaking membership numbers and polling for the Greens. How did Polanski end up being propelled to power on an unprecedented mandate within the membership of the Green Party? And what can he achieve from this position? The Green Socialist examines the Greens through the lens of their tensions, limitations, and contradictions, demonstrating that Polanski is the natural culmination of the party's story so far and that it can serve as a vehicle for transformative politics capable of defeating the far right and building a better Britain.