Objective We sought to evaluate the delays, between-centre variations in practice, and opportunity costs attributable to delays in research governance approval of clinical trials in the United Kingdom. Design Retrospective survey. Setting Research and Development (R&D) departments at 50 UK National Health Service hospital trusts governing 57 hospital sites. Participants R&D departments participating in four randomized multicentre clinical trials coordinated by our Neurosciences Trials Unit. Interventions None. Main outcome measures Median delay between application and research governance approval. Results Only half of the R&D departments used the UK online R&D form. Only a single copy of the application was required by 96% of R&D departments. The median delay between application and research governance approval was 44 working days (inter-quartile range 23-80). A delay of > 20 working days was incurred by 43 applications (75%), of which 24 (56%) were not explicable and 11 (20%) were attributable to local funding negotiations. Based on the trial randomization rates at each Centre, 108 patients (17% of all patients randomized) could have been randomized during the delay, at a crude cost to funding agencies of 253,743; if a four week delay was deemed acceptable, 75 patients (12% of all patients randomized) could have been randomized during unacceptable delays, at a crude cost to funding agencies of 237,700. Conclusions The UK research governance system incurs unacceptably long and costly delays for clinical trials. Urgent reform is needed, including rapid design and uniform implementation of the ‘bureaucracy busting’ measures in Best Research for Best Health.