At the end of January 2017 site clearance started for a new residential tower block complex to be built between Valentia Place and Gresham Road. The vaulting structure of the high level “Atlantic line” viaduct was thus revealed for the first time for most local people.
The Brixton/Loughborough Junction railway track was built after the 1862 South London Act of the London Brighton and South Coast Railway, but the tracks had to be “doubled up” after the London Chatham and Dover Railway also became involved. A viaduct at high level was then needed to pass over the Victoria-Orpington line (and also to pass over the Ludgate to Herne Hill line at Loughborough Junction).
The parapet of the viaduct has regularly placed brackets which appear to be remnants of overhead power gantries. AEG of Berlin was awarded the contract to electrify the line in 1905. Overhead electric trains operated on the high level line from 1909 until 1928, when the line was standardised to 3rd rail DC power as used on the rest of the Southern Railway. A detailed history of the lines can be found here: South London Line and its Traffic and here: “Ups and Downs of an Elevated Line”
Below is a diagram of the South London Line from 1921: