I'd go with fish and chips.
Most of the curry that I've eaten in London has been formless glop, but it is at least possible to find Indian restaurants that cook nice ingredients well. It's also possible to find nice Vietnamese food, but, for the life of me, I've not found Chinese food that lifts itself above the primeval soup with greasy rice stage for a long time. If anybody has a recommendation for Chinese in south London, then please share it.