Lines have now reopened following an earlier trespass incident between Willesden Junction and Clapham Junction.
As service recovers, trains may still be cancelled, delayed by up to 30 minutes or revised.
Disruption is expected until 16:00.
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.