From the Wikipedia page [1]

The Royal Docks Heritage Railway, endorsed in 2006 by Newham London Borough Council, was proposed to open during 2007, taking over the North Woolwich Old Station Museum and the closed section of the North London Line between Custom House and North Woolwich railway stations. Rather than concentrating on the Great Eastern Railway, it would have shown the heritage of local and suburban National Rail lines in London and the south east.

The idea was to re-double the track between stations and run heritage train services and training trains. At closure, North London Line services used only one track, but the second track was in place for much of the route. The line might have been Britain's first mainline electric preserved railway. The 1980s station building was to be the public entrance to the museum site. The official website [2] includes details of the visions for the museum plus pictures of the line, taken from a special train run the day after the last public service ran.