Delivery of intervention and intervention adherence A staggered start was used to facilitate the running of the first set of classes in both Newcastle and Glasgow. This enabled those for whom the GP confirmation of eligibility had not been returned promptly to start at any time within the first three weeks and continue to complete the twelve sessions. In Newcastle, a third set of classes was provided for those who had been recruited later, or whose eligibility checks took a long time to complete. In Glasgow, the class sizes were six and nine respectively and, in Newcastle, class sizes were six, five and four respectively. Four withdrew completely from the study and attended 0, 2, 3 and 11 classes prior to withdrawing. One participant died while in the trial, after attending 6 exercise classes. One participant withdrew from the intervention after 3 classes but continued to provide trial data. Two additional participants randomised to the intervention arm did not attend any classes as their GP consent was not received in time, but ontinued to provide follow-up. Despite this, 76% attended 9 or more classes, which was one of thefeasibility criteria for a future trial. Table 4 summarises the number of sessions attended by participants randomised to the intervention arm on the basis of class registers, and how often they exercised at home (self-report) with its frequency and duration. It can be seen that on average they spent 50 min per week,though there was a large variation in the amount of timespent exercising. This was much less than the 2 h per week that they were encouraged to so.