A fault on a train between Watford Junction and Milton Keynes Central means that some lines towards Watford Junction are currently closed.
As a result, trains may be cancelled, delayed by up to 20 minutes or revised.
Disruption is expected to continue until 15:00.
Advice for Avanti West Coast customers:
If your train is cancelled, your ticket will be valid on the Avanti West Coast train immediately before or after the cancelled one.
Advice for London Northwestern Railway customers:
Tring services are currently unable to operate.
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.