Lines have now reopened following an earlier fault with the signalling system between Alexandra Palace and Potters Bar.
As service recovers, trains may still be delayed by up to 15 minutes.
We anticipate disruption will continue until 14:30.
Customer advice:
Services running from London towards Welwyn Garden City will be subject to delays of up to 15 minutes in the Potters Bar area.
You can continue to use your normal route, but trains will be running at reduced speeds meaning journey times will be extended.
Please check before you travel and you can view the live map here.
Can you tell me more about the incident?
There was an earlier signalling fault in the Potters Bar area which was impacting services travelling towards Welwyn Garden City.
This has now been rectified and services can now run as booked.
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.