Question: Find the names of the trains that do not pass any station located in London.
SQL: SELECT T2.name FROM train_station AS T1 JOIN train AS T2 ON T1.train_id  =  T2.train_id WHERE T1.station_id NOT IN (SELECT T4.station_id FROM train_station AS T3 JOIN station AS T4 ON T3.station_id  =  T4.station_id WHERE t4.location  =  "London")