Input (grade 13): The replacement program proceeded swiftly until 1940, when the last pre-war conversion occurred, leaving only the South London trams and the subway routes 31, 33 and 35, the only tram routes operating into North London to survive the war.
Output (grade 5): In 1940, the last tram conversion took place before the Second World War. This left only the South London trams and subway routes 31, 33 and 35 running.