Complex sentence: The ultimate British 0-6-0 was the Q1 "Austerity" type developed by the Southern Railway during the Second World War to haul very heavy freight trains: it was the most powerful steam 0-6-0 design produced in Europe.
Split into simpler sentences: The ultimate British 0-6-0 was the Q1 "Austerity" type developed by the Southern Railway during the Second World War to haul very heavy freight trains. It was the most powerful steam 0-6-0 design produced in Europe.