This paper examines how political events that harden political identities can shape consumer behaviour. We study the impact of the Brexit referendum in the UK on consumer choices between UK and EU products. Using a unique panel dataset from a major retailer in the UK with over half a billion shopping trips for 12 million shoppers before and after the referendum, we find that consumers respond to the referendum results by increasing consumption of UK products and reducing consumption of EU products. These effects are particularly strong when the UK flag is saliently displayed on the product. We find significant heterogeneity in responses both across shoppers and across product categories. Shoppers switch consumption patterns selectively, driven by a combination of economic, social and political factors. We then use over 13 million tweets related to Brexit during the period around the referendum to examine the mediating role played by social media in shaping identity.