After acquiring the Great Northern & City Railway (GN&C) in 1913 (the current Northern City Line), the Metropolitan Railway considered proposals to join the GN&C to the Waterloo & City or to the Circle line, but these never came to fruition.
Efter at have opkøbt Great Northern & City Railway (GN&C) i 1913 (den nuværende Northern City Line), havde Metropolitan Railway planer om sammenslutning af GN&C til Waterloo & City eller til Circle line, men disse blev aldrig realiseret.