I seem to recall seeing a Tube map from around 2013-2015 that had some (but not all) National Rail stations on it, and that it had a line with double blue lines (similar to the Mildmay line but a bit darker) that travelled in various disconnected sections.
Did it exist? I don't know, but the memory is too vivid for it not to be in some for real, even if it was just some strange fan-made map I saw once.
Some lines I remember being on the map:
Beckenham Junction -> London Bridge but only with the stations that were already on the Tube map at the time (like Crystal Palace and Peckham Rye)
Northern City Line (in full)
Lewisham -> London Bridge
Romford -> Upminster (but for some reason the Weaver Line, well actually its predecessor, wasn't on this map)
Did it exist? I don't know, but the memory is too vivid for it not to be in some for real, even if it was just some strange fan-made map I saw once.
Some lines I remember being on the map:
Beckenham Junction -> London Bridge but only with the stations that were already on the Tube map at the time (like Crystal Palace and Peckham Rye)
Northern City Line (in full)
Lewisham -> London Bridge
Romford -> Upminster (but for some reason the Weaver Line, well actually its predecessor, wasn't on this map)