The Midland main line is to close south of Leicester at around lunchtime on 19 July due to predicted extreme temperatures and their effects on track and overhead line equipment.
No Thameslink or Great Northern service ran north of London, while East Midlands Railway is running a very limited service between Derby/Nottingham and London in the morning. No Corby-London trains are operating.
Network Rail says a limited service to and from London could resume from around 19.00 if temperatures cool enough, adding that it will monitor the track north of Bedford and may need to apply short notice restrictions if rail temperatures exceed 60 degrees.
With the hottest temperatures expected on the East Coast/Midland main line corridors, no trains will run on the East Coast route south of York and Leeds from 12.00 to 20.00 on 19 July.
Operators around England and Wales applied speed restrictions and cut services in response to the high temperatures and warned passengers only to travel if absolutely necessary.