A safety inspection between London Paddington and Heathrow Terminal 5 means a reduced service will run between these stations.
Disruption is expected until 14:00.
Alternative travel advice:
Advanced ticket holders will be able to use their ticket on later services today.
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.