Aldersgate & Barbican station between Moorgate and Faringdon - the tracks are curving to avoid Smithfield Market.
Note an early use of 'zig zag' weld to build up the running rail surface (see turnout in foreground).

This was used to ensure track circuits will operate when "shorted" by train wheels. Usually found on infrequently used sections of line where a build up of rust/muck would otherwise make the correct operation of tack circuits unreliable.