Network Rail is to be prosecuted over the 2007 Cumbrian train crash which left one woman dead and 86 passengers injured.
The Office of Rail Regulation (ORR) has started criminal proceedings against the firm for a breach of health and safety law that caused a Virgin Trains London to Glasgow service to derail near Grayrigg.
Passenger Margaret Masson, 84, was killed and 86 people were injured, 28 seriously, with earlier investigations as well as an inquest last year concluding that the incident was caused by a poorly maintained set of points.
The company is being charged under section 3(1) of the 1974 Health and Safety at Work Act due to a "failure to provide and implement suitable and sufficient standards, procedures, guidance, training, tools and resources for the inspection and maintenance of fixed stretcher bar points".
The stretcher bars hold the moveable rails a set distance apart when the points are operated.
ORR railway safety director Ian Prosser said: "We have conducted a thorough investigation into whether criminal proceedings should be brought in relation to this derailment which caused the death of Mrs Masson and injured 86 people.
"Following the coroner's inquest into the death of Mrs Masson, I have concluded that there is enough evidence, and that it is in the public interest, to bring criminal proceedings against Network Rail for a serious breach of health and safety law which led to the train derailment.
"My thoughts are with the family of Mrs Masson and those injured in this incident. The ORR will do everything it can to ensure that the prosecution proceeds as quickly as possible."
The first hearing is due to take place at Lancaster Magistrates' Court on February 24. Network Rail network operations managing director Robin Gisby said the Grayrigg derailment, on February 23 2007, was "a terrible event".
He added: "Network Rail has not hidden from its responsibilities. The company accepted quickly that it was a fault with the infrastructure that caused the accident. We again apologise to Mrs Masson's family.
"Since the derailment, we have worked closely with the authorities, conducted comprehensive and detailed investigations and made substantial changes to our maintenance regime."
Yesterday Mrs Masson's son George, 62, a retired engineer from Glasgow, welcomed the decision but said he had not been able to move on from the death as he was yet to receive a personal apology.
"I'm over the moon and just hope that justice is done," he said. "I'm going to attend the prosecution with other family members if they let the public in.
"Hopefully, this will bring an end to it, but it would've been all done for me if they had apologised to me face to face. I'd have maybe let go then, but we've never had that from them. All we needed was an apology.
"I was told after the inquest that the directors would come within a couple of weeks and speak to us and apologise personally, but that's two months now and there's still no word from them.
"If they had done it at the time I would maybe have accepted it, but it affected me badly, my health went downhill, I lost nine stone in weight. It brought a hell of a lot of stress to the family and they've not realised how much it hurt, and still don't even realise."
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