Train hit trolley left on track at more than 100mph in Oxfordshire
A passenger train travelling at 123mph (198kmh) smashed into a trolley left on the tracks by engineers who had been working overnight.
The Great Western Railway train from London Paddington to Swansea dragged the trolley for 1.5 miles (2.4km) when it struck it at 06:09 BST near the old Challow station in Oxfordshire.
No passengers were injured and the train did not derail on 21 October.
A Rail Accident Investigation Branch (RAIB) investigation is under way.
The RAIB said a preliminary examination found the trolley was inadvertently left on the line following engineering work.
The inquiry will look at the processes in place for the training, competence and management oversight of staff who were involved.
The trolley's handle became lodged underneath the train, causing damage to the underframe, while the track suffered minor damage. The trolley was destroyed.
Investigators are also looking at a similar incident at about 05:55 on 8 September when a train travelling between Staines and London Waterloo struck an engineering trolley on the approach to Twickenham station.
The trolley had also been left on the track after overnight work.
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