A Network Rail Kent and Sussex spokesperson said they are experiencing ‘serious’ signalling problems on the railway between Honor Oak Park and Forest Hill.
The problems are impacting Transport for London, Southern Rail and Thameslink trains, according to the spokesperson.
At 4.56pm the spokesperson said, “All trains are being squeezed onto two tracks (out of four) to keep them moving - but there are major delays as a result.”
Southern Rail added, “You’ll need to allow plenty of extra time to complete your journey.
“Your train may be cancelled or delayed so you’ll need to plan ahead.”
According to Southern Rail, engineers are working to fix ‘a number’ of signalling faults.
A spokesperson from Southern said the incident is leading to cancellations across their network.