A fault with the signalling system between Crowborough and Uckfield means all lines are blocked. As a result, no trains can run between these stations.

Disruption is expected until approximately 10:00.

Customer advice:

Please allow an extra 30 minutes for your journey this morning as you will have to take an alternative route, or use rail replacement buses when sourced.

Services that usually run between London Bridge and Uckfield will run between London Bridge and Crowborough only.

Ticket acceptance

You can use your ticket on the following, at no extra cost:

• Southeastern between Tonbridge / Tunbridge Wells and London
• London Underground via any reasonable route
• Alternative Southern services between Tonbridge / East Grinstead / Haywards Heath and London
• Brighton & Hove Buses Regency routes 29/29A/29B/29X between Lewes, Uckfield, Buxted, Crowborough, Eridge, and Tunbridge Wells
• Compass on routes 261 between Uckfield and East Grinstead (runs every 2 hours)
• Compass on routes 31/31A/31B between Uckfield and Haywards Heath (hourly service, 45-minute journey)

Replacement buses:

Southern have requested buses from their suppliers, but haven't had confirmation of these yet.

If they can provide a bus service, we'll let you know by updating this message.

Bus journeys will take longer than your usual train journey on this route, and if we can, we'll provide a time estimate here.

Planning your journey:

Live departure boards can be found here.

You can view a live map of the network here, and you can also see our alternative route guide here.

If you're travelling in the London area, you can plan journeys on alternative routes by using the TfL Journey Planner here. You can also use our Southern app to find up-to-date information.

Can you tell me more about the incident?

A track circuit failure will disrupt your journey in the Uckfield area.

This part of the network uses track circuits to detect the position of trains. These are electrical systems which monitor whether a train is on a section of track. They operate as part of the signalling system, which is designed to be "fail safe".

When a track circuit fails, the signalling system will interpret this as a train remaining in place, even though there may not be a train present at all, or the previous service may have long since left the area.

As a result, further trains cannot be automatically allowed onto the relevant section of track. Train drivers will be stopped by red signals on approach. They will then get verbal permission from the signaller so that they can proceed, and will run at a heavily-reduced speed as far as the next signal. This is so that the drivers will stop safely if they see anything ahead of them.

In some areas, the sections between signals can be several miles long, so this can result in delays building up. Even with shorter sections of track affected, there would still be a delay of at least a few minutes to each journey.

Track circuit faults can be caused by a number of different issues, including electronic faults or obstructions on the track. Network Rail manage the signalling system, including track circuits, and their staff will be investigating as quickly as possible. We're closely monitoring progress updates, and we'd like to thank you for your patience.

Check before you travel:

You can check your journey using the National Rail Enquiries real-time Journey Planner.

Compensation:

You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.