Flip-flops are the control group in Britain's office dress debate: the item that did not become acceptable while almost everything around it did. In YouGov's June 2026 survey of 2,075 British adults, 28% called flip-flops acceptable office wear and 67% called them unacceptable. In the very same survey, sandals were accepted 69% to 26%, and men's shorts 68% to 27%, up from 37% acceptance a decade earlier. That comparison rules out the obvious explanations. The objection cannot be to bare feet, because sandals expose as much and pass easily, and it cannot be to informality in general, because informality is exactly what has been winning. The judgement attaches to the specific shoe, which in Britain reads as beach rather than summer office. The survey's remaining refusals point the same way: vest tops were rejected 58% to 35% and midriff-exposing tops 65% to 30%. The items that moved are the ones that cover the same amount of skin in a different shape.