How did the stock market react to the Brexit referendum of June 2016? This column shows that initial stock price movements on the day after the Leave vote were driven by fears of an economic slowdown in the UK and by a sharp devaluation of the pound. Later movements following two speeches by Theresa May in October 2016 and January 2017 were more closely correlated with potential future changes to tariffs and non-tariff barriers on UK-EU trade. This indicates that these speeches led investors to update their assessment of the likelihood of a hard Brexit.