A man was hit and killed by a train on Thursday morning after escaping from a custody vehicle travelling to a court hearing.
The man, in his 40s, escaped the transport contractor's vehicle as it was stationary on the A1, according to a joint statement from Hertfordshire Police and British Transport Police (BTP).
He escaped during an altercation in which two security guards were injured, while the van was pulled over on the hard shoulder around 9am, having left the custody suite at Stevenage police station.
BTP performed a search of the area, and a casualty was discovered on the track near Welwyn North station around 9.40am.
Formal identification of the body has not yet taken place, but police have said that the man's family had been made aware of the incident.
The forces said that the two members of transport contractor staff were taken to hospital for treatment for their injuries, which are not thought to be serious.
Hertfordshire Police has referred the incident to the Independent Office for Police Conduct, and a file has been prepared for the coroner.
Inquiries are underway "to establish the full circumstances and officers will remain in the area while initial investigations continue", a police spokesperson.
Local resident David Elsdon, 82, said that he had never seen so many police before and it "was all a bit of a shock".
He told the BBC: "We were just out the front ready to leave for the town and inundated with a number of police cars coming along.
"I think we passed 10 in total before we got out on to the main road."
The incident sparked travel chaos in London throughout Thursday.
Thameslink, LNER and Great Northern trains from London through Hertfordshire, Peterborough and Cambridgeshire were severely delayed, and some delays and cancellations are still occurring despite the lines reopening on Thursday afternoon.
A Thameslink spokesperson confirmed that one of its trains had been involved in the incident, and advised people to check their route before travelling.
