In July 2024, the UK will have a general election and elect a new government. The election campaign is filled with claims and counterclaims about what different parties will do. The promises made in political manifestos are a key part of this claim-making, and the wider electoral processes which aid voters in making their decisions. Manifestos can be an important part of people’s decision making and are one way in which the elected government is then held to account. However, the level of detail varies across manifestos, and the accuracy of costings and other information is hotly contested. This work assesses the pledges made in manifestos using a complex system modelling approach, identifying how different pledges interact to predict how each party’s policies would change the political, economic, environmental, and social landscapes of the UK. The outcomes show that more radical ideas are proposed by the smaller parties. The Greens and Liberal Democrats deliver better environmental, social and public services outcomes. Reform UK are predicted to cut average living standards (despite tax cuts) and perform poorly on the environment and many public services such as the NHS, but likely to reduce crime. The Labour and Conservative parties have policies which mainly are predicted not to deliver to the same magnitude as the Greens, Liberal Democrats and Reform (as indicated above). However, Labour are more aligned in most cases to publicly favourable outcomes than the Conservatives. While no party is a clear ‘winner’ in terms of policies, this work compares outcomes across the different parties and may result in better informed decisions being made at the ballot box.