Minimising the risk of preventable harm to patients is a National Health Service (NHS) priority in the UK. In the past decade, a patient safety agenda has been established in many secondary care, but is only now migrating to primary care. Information about the epidemiology of error, contributory factors and the scale of preventable harm is limited in comparison to what is known in acute hospitals. We describe how to apply a recently developed trigger tool - a rapid audit method of screening electronic patient records to detect patient harm - as a feasible part of routine primary care practice. We promote the idea that the trigger tool approach will enable care teams and clinicians to refocus their learning and improvement efforts on one of the most serious issues facing the NHS or any modern healthcare system - how to minimise the risks of unintended but avoidable harm to patients.