Durham

It's never a good idea to have two questions with the same answer – even if one of them is a supplementary (see my comments passim about supplementaries being as important as any other question, if not more so).

Durham's congestion charge is directly linked to its World Heritage Site, and it's not beyond the bounds of possibility that this might have been a subject for discussion, had the supplementary in the previous round been used for any reason. Not only that, but people just don't expect two questions with the same answer, and anyone who had to think of an answer to this question (to guess, if you like) might well have ruled out Durham for this reason.