Lines have reopened following a fault on a train between Milton Keynes Central and Watford Junction.
Trains running between these stations may be delayed by up to 30 minutes.
Disruption is expected until 09:00.
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.