Terrorist attacks have often been found to impact voting behaviours in the country of the attack. Here I study the impact of 9/11 terrorist attacks in New York on voting preferences in the UK, concluding that 9/11 impacted the voting intentions of the British, significantly increasing prospective votes for the Conservative party and reducing future votes for the Labour, the incumbent party at the time. Using daily survey data on voting intentions of a representative sample of several thousands of British people in the days before and after the 9/11 attack, taking a Regression Discontinuity Design and Event Study approach, reveals an immediate large increase by about 31% in intentions to vote for the Conservative party and a decline of 17% in prospective Labour votes at future elections. These findings are robust to several checks, with the effects being short-lived, and varying largely depending on previous voting decisions, as well as by gender, education and employment status.