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.
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A damp and cold night ahead. Valentine's Day will start cloudy but become brighter in the afternoon. Risk of showers along the Kent coast.
Cold and damp tonight with outbreaks of rain. A cold and dull start to Valentine's Day but becoming drier and brighter by the afternoon.
Rain turning more patchy this afternoon but more persistent along the coast. Feeling cold in the brisk north-easterly wind.