However, to date there have been no large RCTs of the classes and NICE has identified a need for such studies with a health economic component to be completed. We have, therefore, recently undertaken a pilot RCT using the same design as the current application. This has allowed us to test and be confident of our recruitment process, establish power and test the delivery of the intervention and research. In a previous pilot in Glasgow and Northern Ireland (with course delivery by the charities AOD and AWARE), we successfully screened and randomized 53 participants using the same planned recruitment strategy. Mean differences at the primary follow-up point (3 months) have informed our power calculation (see below).