A derailed locomotive was left a “sitting duck” for seven minutes before a high-speed intercity train crashed into it because of a “major flaw” with signals, it has been claimed.
The incident happened near Salisbury station in Wiltshire on Sunday night when the rear carriage of a Great Western Railway (GWR) service from Portsmouth Harbour to Bristol Temple Meads derailed.
Minutes later a South Western Railway (SWR) service from London to Honiton, Devon, crashed into it after signalling was damaged.
At least 17 people were injured, with passengers being thrown around pitch-black carriages.
Families out trick or treating for Halloween near Salisbury station heard a huge bang “like a bomb going off”.
Firefighters and paramedics rescued around 120 people, including a three-week-old baby girl.
In a statement late on Sunday, BTP confirmed there were no fatalities, but a “small number” of people, including the driver of one of the trains, were taken to hospital to have their injuries assessed.
One of the drivers was cut free having suffered a suspected broken ankle.
A senior Network Rail engineer told MailOnline that when the GWR service derailed, there should have been an automatic obstruction warning to stop any train entering the same mile-long stretch.
They said: “There has been a major flaw within the signalling system within Network Rail. The system says that the line is not safe for the passage of another train because there is an obstruction on the line.
“According to my system, the signalling system was aware seven minutes before impact. It should’ve automatically stopped the train. It should’ve automatically set all signals to red.
“If the driver didn’t see the signal, the system should’ve made the train stop.”
A passenger said: “It was really scary. We were a sitting duck. Lots of people started making phone calls to their families because we thought we were going to die.”
In a statement, Great Western Railway said the line would remain closed today as “specialist teams continue their investigations”.
Transport Secretary Grant Shapps tweeted: “My thoughts go out to those affected by the serious rail incident near Salisbury.”
He said the Rail Accident Investigation Branch and Office of Rail and Road were investigating, adding: “We need to understand how this happened to prevent in the future.”
Claire Mann, managing director of South Western Railway, said it is “too early to speculate” about the crash.
Transport Salaried Staffs Association general secretary Manuel Cortes said the incident was “a very sobering reminder about why safety on our railways is always paramount”.
British Transport Police said an investigation was underway into the train collision.
A statement released on Monday read: “At around 6.45pm, a Great Western Railway service from Southampton to Cardiff collided with a South Western Railway service from London to Honiton as they both entered the Fisherton Tunnel in Salisbury.
“Both trains were travelling in the same direction and one train struck the side of the other, causing it to derail whilst in the tunnel. The front few carriages remained upright while the back tipped on their side.
“Ninety-two passengers were on both train services. Around 30 people attended a casualty centre which was set up in a nearby church, the majority of who were walking wounded and assessed at the scene.”
It said 14 people were taken to hospital by ambulance where they received treatment for minor injuries.
“Unfortunately, the driver of the train was more seriously injured and his injuries are believed to be life-changing. He remains in hospital in a stable condition this morning, and his family have been informed.
“We have now moved out of the rescue phase of the operation and into the investigation which will involve the trains remaining in situ for some time. The investigation remains at an early stage but a senior detective has been appointed to lead the enquiries as we work to establish the full circumstances of how this incident came to happen.
“This will no doubt have been an incredibly frightening experience for all those involved and our thoughts are with them and their families today.
“Specialist officers and detectives remain on scene in Salisbury and we are working closely alongside the Rail Accident Investigation Branch (RAIB) and the Office of Rail and Road to establish exactly how these two trains came to collide.
“We are keeping an open mind but at this early stage there has been nothing to suggest the train struck an object or that there was any significant delay between the trains colliding and then one derailing.
“This has been a large scale, multi-agency operation and I would like to pay particular to thanks to our emergency service colleagues for their efforts in safely evacuating passengers, and to the many members of the local community who reached out with offers of help.”