A problem with a signalling system at Mottingham is forcing Southeastern Railway to cancel trains.
The train company posted on its website that because of the problem, journeys between Crayford and Hither Green are being disrupted.
"This process is causing delays of 10 - 20 minutes to trains, and as a result, some services will be altered, or cancelled at short notice," the message said.
"Signalling problems between Lee and Mottingham mean that signalling staff need to manually direct train services through a set of signals."
Southeatern said that the disruption is expected until 8am, but could go on for longer.
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