wrote

What happened to the side track at Highbury & Islington?

The AC lines between Dalston Kingsland and Camden Road are currently OOU and
under engineers' possession, with some sections lifted. Eventually the
existing DC pair will be used by the ELLX between Dalston Junction and
Highbury & Islington, while the NLL service and freight will use the
reinstated northern pair, using 25 kV AC OHLE. Between Highbury & Islington
and Camden Road (exclusive) there will be 4 tracks, effectively a pair for
the NLL passenger service and long up and down goods loops. Canonbury and
Highbury & Islington will each have 4 platforms (2 for ELLX and 2 for NLL),
while Caledonian Road will have 3 (the existing eastbound platform
reinstated as an island).

Peter