The North London Line is not what it used to be! Recent talk of stabling on the Richmond branch reminded me of the huge Gunnersbury station site hidden beneath the current 1960s development here. Dalston Junction remained untouched until around that time also, with platforms spread on both west and east sides of the triangle! Here All hidden today! (I didn't find any more recent photos showing all platforms.)
The lines on the left were the connection to the LSWR Chiswick loop with a connection towards Hounslow. these would have been used by trains from Waterloo to hounslow via Clapham Junction, Addison Road, shepherds Bush, Hammersmith Grove Road and Turnham Green. That line between Addison Road and Hammersmith closed during WW1. The viaduct between the current District and Picc Lines in the lasting memory of it, as is the bump in Brook Green Road near the junction with Shepherds Bush Green.
When Overground services were planned to return to Dalston Junction, it was felt wise to retain the eastern route towards Hackney and Stratford for a possible future service. However, the current platforms must be sited south of the original to straighten them, so that retained access to the eastern curve can be seen opposite the southbound through platform at around the mid-point! How could this possibly be used for a future service, since both directions would need to work single-track through the southbound platform, without stopping at the station since access is part-way along. All this whilst not disrupting the current through service!