A train goes past houses in St Albans (Image: Archant)
There are no services between London St Pancras and Luton.
A person has been hit by a train so the line has been closed for safety reasons.
Trains may be cancelled, heavily delayed or revised.
The disruption is expected to last until the end of the day.
If you would like to follow this incident on Twitter, use #Radlett.
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