Within a week of the tragedy, British Transport Police knew exactly how the men had died.
Tests found the brakes on the runaway wagon were faulty. In fact, they had been deliberately disconnected.
As survivors were signed off work as they struggled with the trauma of what they had seen, the fast-moving inquiry became a criminal one.
On March 2, officers arrested Mark Connolly, then 42, the boss of Anglesey-based MAC Machinery Services, and his 27-year-old colleague Roy Kennett, of Maidstone, Kent. Connolly’s company had been sub-contracted to work on the £6 billion upgrade of the West Coast Main Line and both were involved in the removal of track from the line in Cumbria.
The pair were questioned on suspicion of the manslaughter of the four men before being released on bail.
It was not until October 2004 that British Transport Police charged them both with four counts of manslaughter.
They made a preliminary court appearance in Kendal the following month and eventually stood trial at Newcastle Crown Court in January 2006 – nearly two years after the deaths.
Families had waited a long time for answers as to why their loved ones had been so suddenly taken from them.
And they were about to get them, as damning evidence demonstrating disregard for safety and financial greed was laid bare to a packed courtroom over seven weeks.
To save money and make it look as though everything was above board, Connolly disconnected the wagon’s brakes when they stopped working properly. He put ball bearings into faulty brake cables, rather than pay to have them fixed.
He earned hundreds of thousands of pounds yet the cost of the repairs would only have been a few hundred pounds, police said.
Kennett placed pieces of wood under the wagons’ wheels in a flawed bid to stop them running away while they were loaded. He also used a crane he was not qualified to operate. But the wood was no substitute for functioning brakes. It was crushed by the first wagon’s wheels and it began to roll away.
Frantic attempts were made to stop it, but it was too late. With no alarm system in place to warn the workers carrying out unrelated work in the dark in Tebay, their fate was sadly sealed.
Retired railwayman Tom Burgess, whose son Darren died in the accident, said of the trial: “It was really distressing. It was purely driven by profit because Connolly wouldn’t pay for these repairs.
“It was terrible the waste of life that it caused. I felt very bitter. It made it worse as it could have been avoided.”
His wife Christine added: “I was very angry. We still feel bitter now after all this time. Connolly wouldn’t even give evidence, which shows what kind of a man he was. There didn’t seem much remorse from either of them. When he was asked in court if he could have done anything different, all Kennett could say was that he wished he never got out of bed that day.”
Connolly and Kennett were found guilty of manslaughter through gross negligence, plus breaches of health and safety law.
In March 2006, Connolly was jailed for nine years and Kennett for two.
With anger evident in his raised voice, Craig Johnston, regional organiser for the RMT Union north, said ahead of this weekend’s anniversary: “They were dodgy workers who brought dodgy equipment onto the rail network, resulting in four of our members being killed.
“It was a shocking indictment on the rail industry and a disgraceful and shameful episode in the history of our railways. I just can’t get over the shortcuts that were made in railway maintenance. It was appalling.”
Tebay reopened the debate about the privatisation of the railways, with unions arguing that contracting such a vast number of companies to work on the network had caused the “fragmentation” of the industry and lowered safety standards.
Even before Tebay, Network Rail had started bringing all maintenance work in-house after a string of fatal rail crashes since the late 1990s, ending the practice of smaller firms being contracted to repair the infrastructure.
All such projects are now understood to be carried out by Network Rail staff, but some remain concerned that renewal work – the installation of new track – is still contracted to outside companies. Mr Johnston added: “The whole industry needs to be put back together again. The whole issue surrounding Tebay was letting private contractors and sub-contractors onto our railway and it’s still going on.”
Mr Burgess agreed. He said: “Tebay wouldn’t have happened in the days of British Rail because everything was done in-house - plumbers, electricians, everything – there was no outside contracting like there is now.
“It was a mistake to privatise it all - all it’s done is make a lot of money for different contractors in my opinion. If there had been the same funding given to British Rail that has been given since, it would be a far better set up.”
A year after Connolly and Kennett were jailed, the pair appealed against their convictions, but this was rejected by top London judges.
Connolly did, however, win a two-year cut in his sentence and ordered to serve seven years - but we can reveal he served even less than that.
Mr Burgess said: “He served less than three years. The police came and told us he had been released on a tag. Even if they had got the full ten years that they could have, for four lives and the misery it has caused for all the families, what punishment is that?”
The Ministry of Justice refused to comment.