jats:titleAbstract</jats:title>jats:sec jats:titleObjectives</jats:title> jats:pThis note describes a free online portal (<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.therandomiser.co.uk">www.therandomiser.co.uk</jats:ext-link>) that allows researchers to design randomised controlled trials and then delegate the random assignment process to pracademics delivering the experiment.</jats:p> </jats:sec>jats:sec jats:titleMethods</jats:title> jats:pObservation of the use of this tool in repeated randomised trials in police agencies.</jats:p> </jats:sec>jats:sec jats:titleFindings</jats:title> jats:pResearchers are able to design RCTs using the online portal, which offers many ways to customise the experimental design. Results are downloadable in excel or plain text format. Researchers can grant access to treatment providers, enabling them to log in securely, enter identifiers for cases, and assign different treatments to each case. Email notifications of assignment can be sent to designated list of recipients who can track the allocation of treatments. This tool delivers this functionality at zero cost and at the time of writing is being used by 78 researchers, who have set up 70 experiments that have processed 5778 randomisations.</jats:p> </jats:sec>jats:sec jats:titleConclusions</jats:title> jats:pTheRandomiser has been used in multiple experiments with feedback suggesting it is a powerful and user-friendly tool. The ability to deliver trickle-flow randomisation with high degrees of researcher control are attractive, as is the ability to edit an unlimited number of qualification questions prior to randomisation.</jats:p> </jats:sec>