It follows a campaign by commuters for a later rush hour service in the evening to help ease overcrowding.
Other Thames Valley services will have more carriages with first class compartments converted for use by standard ticket holders. There are also extra trains between Swindon and Westbury.
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Monday afternoon's weather for the east of the region
Monday afternoon's weather for the west of the region
Two men involved in the supply of Class A drugs in Tunbridge Wells have been jailed for more than nine years.