It is the beginning of the end of paper rail tickets for some Southern passengers travelling into London.
Commuters using the Brighton line into the capital will be able to use smart-cards, similar to Oyster-cards, at East Croydon, Clapham Junction, London Victoria and London Bridge.
The scheme will be widened out to all London stations as of next year.
Baroness Kramer launched the new scheme yesterday.
More top news
A man has been arrested on suspicion of murder after a 25 year-old woman died in Thatcham this morning.
A number of schools remain closed in Oxfordshire on Tuesday due to icy conditions. The Met Office has issued a weather warning for ice.
Holly has Tuesday's forecast for the east of the region.