Corbynism was the new political thought in town. Its advocates claimed it heralded the end of neoliberalism, the dominant idea that has guided UK policy since its implementation by Margaret Thatcher (see McDonnell, 2018b: x–xii). While the media and scholars scrambled to explain the rise of Corbyn to the Labour leadership and his surprising electoral performance in the 2017 general election, there has been little investigation into what Corbynism substantively meant. It was commonly assumed that Corbynism represented a throwback to the socialism of the 1970s. It was accused of being, what was defined by New Labour during its ascendancy, ‘Old’ Labour (see Seldon and Hickson, 2004). However, was this true? At times, the commentary and analysis on this seemed lazy, which is understandable given Corbyn's political record. Corbyn's opponents frequently referred to Corbyn, and his Shadow Chancellor, John McDonnell, as Marxists. Suggesting they are classic Marxists is far-fetched and the accusation has more to do with political posturing than any concrete analysis. Indeed, under the leadership of Corbyn, there was evidence of engagement with new ideas – or at with least ideas that were seen as radical. The consideration of radical ideas was heightened by the Brexit referendum in 2016, yet this event, let alone the result, threw Corbyn and his allies off course in terms of solidifying their position in the party. It did not, however, drastically alter their thinking. What it did do, though, was bring to the fore the difference over ideas in the left and right of the party; between the different sections of society that vote Labour; and between the Parliamentary Labour Party (PLP) and the leadership. These areas, Corbynism and Brexit, and how they were interrelated, are analyzed in the last two chapters of this book. To comprehensively understand the emergence of Corbynism, both Blairism and (Ed) Milibandism are analyzed in the preceding chapters because they are intrinsically linked to the growth of Corbynism. All three eras represent the changing nature and ideas within the party, as they tried to adjust to their political environments.