Train services are expected to be disrupted until 9pm tonight, following delays between London Euston / Clapham Junction and Milton Keynes this morning.
Safety checks being made on the line between Hemel Hempstead and Watford Junction mean trains are having to run at a reduced speed between Milton Keynes Central and London Euston / Clapham Junction.
London Midland and Southern railways are no longer affected by this, but Virgin Trains will run a reduced service between Manchester Piccadilly / Birmingham New Street and London Euston.
Passengers may be delayed by up to 20 minutes.
More top news
A 21-year-old man from Loughton was arrested at the scene on suspicion of causing death by dangerous driving.
There are few people more dedicated to the Notting Hill Carnival than Allyson Williams - she's sewed thousands of colourful costumes.
Ealing Council as the first to create a buffer zone in April 2018 following demonstrations.