A 56-year-old train driver died after suffering a heart attack as he was driving a train from London to Essex.
Steve Jones had been driving the 8.13pm c2c service between Grays and Barking when the incident occurred.
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When Mr Jones fell ill his foot came off the safety pedal, stopping the train almost immediately, the Standard reports.
When the father-of-two could not be contacted, a driver in the area stopped to help and an ambulance and the British Transport Police were called. Although efforts were made to save Mr Jones' life, he died at the scene.
A spokesman for c2c said: "Every c2c train is designed with a safety system to manage these specific situations, and last night it operated exactly as intended. The train was brought to a controlled stop within seconds and there was absolutely no danger to passengers at any stage."
Trains in the area were halted for over an hour while the incident was investigated: it's thought that 50 trains were affected during this time.
"Thank you to all our passengers for their understanding last night while we helped support the ambulance service and British Transport Police in their efforts."
On hearing the tragic news, colleagues paid tribute to Mr Jones.
Co-worker Mark Daniels said: "He was a great work colleague who will be missed. He will be a character lost from the mess room, but he will be most missed by his family including his two children. RIP Jonesy."