I admit I was surprised when Sturgeon said they were unlikely to be linked to COP26. As a mass event with people travelling from all over the world and limited controls, it sounded like a major risk factor. It's not hard to imagine catering staff or security staff being affected - and as they're likely to be young and relatively fit, perhaps not even symptomatic. Purely speculative at this stage of course, but it's as wrong to discount things as blame them.
Meanwhile, thinking of potential superspreader events: