With collaborators at Chelsea and Westminster NHS Foundation Trust, we estimated the impact of a rapid testing and result notification service for patients testing for sexually transmitted infections at the Dean Street Express clinic. We found that a rapid testing service for asymptomatic infections resulted in 8 days’ faster time to result notification for CT and/or NG which enables faster treatment, thus reducing infectious periods and leading to fewer transmissions, unnecessary partner attendances and clinic costs, compared with those attending an existing ‘standard’ sexual health clinic.