original_query: What were the major extensions of the City & South London and Hampstead lines in the 1920s?
query: What were the major extensions of the City & South London and Hampstead lines in the 1920s?
answer: The City & South London Railway's tunnels were rebuilt to the same diameter as other tubes, extending north to a junction with the Hampstead line at Camden Town and south to Morden.  The Hampstead line was extended to Edgware and south to another junction with the City & South London at Kennington.