Delays are expected on the London Overground between West Croydon/Crystal Palace and Highbury & Islington because of a signalling problem at New Cross Gate station.
The signalling problem has been resolved but there will still be delays until 8.30am.
In a Tweet, National Rail said customers can use their tickets on Greater Anglia, Great Northern, Southeastern, Southern, TfL Rail and Thameslink services to get to their destinations.
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