Recent heavy rainfall led to serious flooding at many stations, including Balham. Maintenance workers put bright green dye in the water supply to identify exactly where the flooding was originating, making the station look like it had been attacked by Slimer from Ghostbusters.
Incidents like this, as well as recent leakage problems at Oxford Circus, show some serious deficiencies in basic infrastructural maintenance. Years of budget cuts and outsourcing of maintenance work can't have helped.
Water way to run a railway!