It was, thankfully, only at a fast walking pace when the wheel came off the hub. I felt something wasn't correct and braked slowly as the last wheel nut was spat out. As you probably read earlier in the thread, I had a quiet word with the Manager in workshop, away from customers. He and the experienced guy who did the job were absolutely mortified. Shiny new nuts arriving Tuesday, so just pottering about locally until then. They didn't try saying I should have checked, that's othe forumites on here. No real damage done. If they'd tried deflecting blame, I'd have taken a totally different approach.