This picture, issued by @SW_Trains, shows the damage to a Wandsworth substation caused by yesterday's lightning strike.
Ouch.
UPDATE: Some more pictures of the damage at Linford St Power Substation from Network Rail...
Linford St supplies power to more than one NR Route (including Wessex and Kent).
Traction power was restored at 22:04 (the lightning strike took place at 17:30) and this morning's peak ran as normal.