Buses are replacing trains between Brighton and Littlehampton/Barnham, due to work being carried out between Brighton and Littlehampton stations.
Great Western Railway services will start from/terminate at Barnham, with buses running between Barnham and Worthing, Shoreham-by-Sea, Hove and Brighton.
On Sunday, the 21.46 Brighton to Portsmouth Harbour service will not run. Passengers are advised to use Southern rail/replacement road services.
There will also be an amended service between Reigate/Purley and Gatwick Airport all day Sunday.
A reduced Southern service is operating between London Victoria and Brighton. Buses will replace trains between Purley and Horley (via Redhill) and also between Redhill and Tonbridge.
A reduced Gatwick Express is running between London Victoria and Gatwick Airport. A half hourly service will operate departing London Victoria at xx:00 and xx:30. A half hourly service will depart Gatwick Airport at xx:20 and xx:50.
Meanwhile the Thameslink 23:10 and 23:40 Bedford to Three Bridges services will depart East Croydon later than normal and arrive Gatwick Airport and Three Bridges up to 20 minutes later than normal.
In East Sussex, buses will replace trains between Ore and Rye stations until 11.20am.
To find out more about how engineering work will affect your journey, visit www.nationalrail.co.uk
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