The prosecution of Network Rail and maintenance company Jarvis Rail over the 2002 Potters Bar rail crash was welcomed tonight by the family of one of the seven victims.
The two companies will be prosecuted for "breaches of health and safety law" and, if found guilty, both could face unlimited fines.
The prosecution, announced by the Office of Rail Regulation (ORR), follows the conclusion of the inquest this year into the deaths at Potters Bar in Hertfordshire where the jury returned seven verdicts of accidental death.
Six people aboard a London to King's Lynn train were killed, along with one pedestrian.
Perdita Kark, daughter of Austen Kark who died in the crash, said: "The only thing that bothers me is why it has taken nearly nine years to get to this point.
"My feeling is that it should have happened far sooner following the crash. We shouldn't have to have fought and fought for so long to get an inquest.
"It's absolutely right and proper. I hope they appreciate why they are being prosecuted and learn from their mistakes."
The other victims were: Emma Knights, Alexander Ogunwusi, Agnes Quinlivan, Jonael Schickler, Chia Hsin Lin, and Chia Chin Wu.
Those who campaigned for a prosecution welcomed today's decision.
Gerry Doherty, leader of the TSSA rail union, said: "It is deeply regrettable that it has taken eight long years and much suffering by the families involved to get to this stage.
"It seems at long last we are going to find just who was responsible for this tragedy."
Bob Crow, general secretary of the Rail Maritime and Transport union said the announcement was "better late than never".
During the derailment, one of the carriages became wedged under the platform canopy at Potters Bar.
The pedestrian who died was struck by debris falling from a bridge on to the road.
A Health and Safety Executive report into the tragedy listed a catalogue of faults which led to the crash on May 10 2002. Loose nuts on the points had caused the crash and earlier inspections had not spotted defects, it found.
The points were not adjusted properly and there was a failure to understand their design and safety requirements, it concluded.
A later report by the Rail Safety and Standards Board, in 2005, said the derailment was caused by parts of the points moving as the train, operated by the West Anglia Great Northern train company, passed over them. One of the stretcher bars, which keep the moveable section of track at the correct width for the train's wheels, had fractured.
At the time of the crash, the company in charge of rail infrastructure was Railtrack whose responsibilities were taken over by Network Rail (NR) in October 2002.
Network Rail said the railway today is "almost unrecognisable" since the days of Railtrack and the Potters Bar tragedy.
"All of the recommendations made by both the industry's own formal inquiry and the Health and Safety investigation have been carried out," it said.
"Today, the railways are safer than they have ever been, but our task remains to build on that record and always to learn any lessons we can to make it ever safer for passengers and those who work on the railway."
Jarvis Rail, the maintenance contractor for the Potters Bar area at the time, went into administration in March this year.
The companies each face a charge under a section of the 1974 Health and Safety at Work Act. In the case of NR, this relates to its alleged "failure, as infrastructure controller for the national rail network, to provide and implement suitable and sufficient training, standards, procedures and guidance for the installation, maintenance and inspection of adjustable stretcher bars (part of the points)".
Jarvis Rail also faces a charge for its role as "infrastructure maintenance contractor" for the relevant section of the track.
ORR rail safety director Ian Prosser insisted everything would be done to ensure the prosecutions proceeded as quickly as possible for the sake of the families involved.
The case is due to be heard, initially, at Watford Magistrates' Court in Hertfordshire on January 7 2011.