My last flight is LHR-DAR on BA, so that cannot be it. I guess the BA people in japan are just lazy or don't know much about RTW tickets and didn't want to do this. It's disappointing though that they didn't want to reissue a BA issued first class ticket for a BA gold card holder. Fortunately cathay were excellent as they always are, but BA ground services were disappointing (which they tend to be most of the time).