Gatwick Express services have been suspended owing to a landslip south of the airport.
The incident, which occurred on Monday (27 January) between Three Bridges and Gatwick airport, has blocked some of the northbound lines.
Gatwick Express services are suspended in both directions, although Southern Rail and Thameslink services – which also serve Gatwick – are continuing to operate.
The operator is warning passengers “it may take at least 10 minutes longer than usual" to reach their destinations, and has advised passengers to allow an extra 30 minutes to complete their journeys.
Trains which usually travel between Bedford and Three Bridges will now run between Bedford and Gatwick airport only. Disruption is currently expected until the end of Tuesday (28 January) while repairs are carried out.
Network Rail South East said: "Our engineers are still working to assess and rectify the damage caused by the landslip between Three Bridges and Gatwick Airport yesterday [Monday].
"Before trains can run on the line again after a landslip, we’ll remove any debris and check that the infrastructure is safe and working."
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