Commuters are facing cancellations and delays of up to 25 minutes this morning following a broken down train in West Norwood.
Services between Tulse Hill and Crystal Palace are being disrupted.
Southern Railway said customers could use tickets on London Buses, London Underground and London Tramlink on reasonable routes throughout south London.
First Capital Connect services between Sutton and Luton are also experiencing delays of up to 15 minutes, with Streatham, Tulse Hill and Herne Hill stations all being affected.
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