Background The London Ambulance Service NHS Trust receives more than one million calls every year, with roughly 10% of these coming from the Metropolitan Police Service. The majority of calls from the police are for patients with non-life-threatening symptoms, to which a clinical response is aimed to be dispatched within 30 minutes. When demand is high, however, ambulances get re-directed to more severely ill patients and police officers end up waiting on-scene for prolonged periods. This has a detrimental impact on the police services' response to calls.

Methods The Joint Response Unit is an initiative designed to address the above problem. It consists of a solo clinician providing a dedicated response to police requests within an assigned borough. Initiated in 2011, it now covers 12 London boroughs, with the hope of further expansion within and outside of London. This evaluation is assessing the necessity and clinical safety of this initiative.

Findings An on-scene clinical response was required for 95% of patients, highlighting the need for the Joint Response Unit. Arrival time to life-threatening calls is improved and conveyance to hospital decreased due to the clinician's ability to appropriately assess, treat and discharge on-scene. Since its implementation in 2012, the Joint Response Unit has reduced police on-scene waiting times from an average of 36 minutes to 7 minutes. Over the course of just one weekend, the faster clinical response equates to a total of 13 hours of officer-time saved.

Conclusions The Joint Response Unit is a unique and successful model of collaborative working between emergency services, with benefits to both the ambulance and police services. Other services should look at replicating this model to enable effective collaboration nationally.