A problem currently under investigation between London St Pancras International and St Albans means trains running between these stations may be delayed by up to 20 minutes.
Disruption is expected until 16:00.
Customer Advice
Services that run in both directions between London St Pancras International and West Hampstead Thameslink/Mill Broadway will be delayed.
You can travel using your normal route this afternoon but please allow some extra time for your journey.
Planning your journey:
You can see a live map of the network here. This will show where your journey is likely to be affected.
You can also use Thameslink's app to find up-to-date information.
Can you tell me more about the incident?
At the moment, Thameslink are working with local staff and colleagues at Network Rail to assess the situation.
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.