The driver, an unnamed 39-year-old from Essex, was held by police “on suspicion of endangering the safety of the railway and being unfit to work on a transport system through drink or drugs.” A British Transport Police statement read: “A 39-year-old man from Essex was arrested on 26 October in connection to an incident at Enfield Town station on 12 October, where a train crashed into the buffer stops.

       “The driver of the train was arrested on suspicion of endangering the safety of the railway and being unfit to work on a transport system through drink or drugs.

       "He has been released on bail until 19th November, and detectives continue to make enquiries into the incident.”

       Reports now allege that a routine blood test revealed the presence of cocaine in the driver’s system.

       It is understood that he has been suspended by his employer, Arriva Rail London.

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       A spokesperson for Arriva Rail London told MyLondon: “We cannot comment on this criminal case, but we can confirm that the driver involved in the low-speed collision at Enfield Town station has been suspended following a positive test for drugs or alcohol.

       "We also continue to provide every assistance to the investigation by the Rail Accident Investigation Branch (RAIB).

       "We have a zero-tolerance policy to drugs and alcohol and will always put the safety of our customers and colleagues first.”

       The crash on 12 October saw the eight-carriage London Overground train derail at Enfield Town station in North London around 8:15 am.

       The service had departed from Liverpool Street approximately half an hour earlier.

       A source has told the Sun: “This has caused shock among his colleagues because it’s a very serious incident.

       “Luckily, by the time the train hit the buffers it had slowed down and somehow managed to stay upright.”

       At the time of the crash, a British Transport Police spokesperson said: “Officers were called to Enfield Town at 8.20 am following reports of a train hitting the buffer stops at the station.

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       “Two people, including the driver, were checked over by paramedics at the scene.

       “As is routine, the driver has been breathalysed and blew negative.

       “We remain on scene while enquiries continue.”

       In the immediate aftermath of the collision, the driver was said to be “in shock” and two people were treated for “minor injuries.”

       General manager for Transport for London’s Overground service, Rory O’Neill, said there will be a comprehensive investigation to “establish how this happened,” calling the incident a “low-speed collision with a buffer.”

       Ellie Burrows, Network Rail's route director for Anglia, said: “The driver is being treated for shock and there are reports of a few minor injuries.”

       The 39-year-old was described as an “experienced” driver.

       A maximum six-month prison sentence is possible if a transport worker is convicted of being unfit for work through alcohol or drugs.

       Two years in jail could be the sentence for endangering the safety of people on the railway.