The report outlines work the RAIB has carried-out so far, including details of an urgent safety advice warning issued in June 2007.
The RAIB are keen to stress that these findings are preliminary, and they have not yet drawn any conclusions. The final report will be released early next year.
A key finding is that nuts at the Lambrigg 2B points, where the derailment occurred, were found to be loose on 7 January 2007. The points were repaired almost immediately, but the cause of the fault was not investigated.
"If any component is found to be loose, broken or requiring adjustment, the cause for it must be investigated." reads Network Rail standard NR/SMS/PF01.
Also, "The undone nuts on 2B points on 7 January 2007, which led to the replacement of the nuts and bolts that day, is believed to be an indication that the condition of the points had started to deteriorate some weeks before the derailment occurred."
The RAIB also suggest that early warning existed, but was not heeded. "The residual gap between the right-hand switch and stock rails at the location of the third stretcher bar had been in excess of the laid down dimension since at least 2004."
The report also has some inconsistencies with the Rail Industry report, issued last month. As described by that report, inspections were shifted to Sunday mornings from weekdays when the speed limit on the line was raised to 95mph. This restricted inspections when the days were short, such as in the winter.
On the morning of 18 February, a supervisor from the Lancashire and Cumbria maintenance area carried out a supervisor’s plain line inspection instead of the scheduled basic visual inspection.
The Rail Industry report claims the supervisor simply stopped his inspection. According to the RAIB report:
"At Lambrigg, the supervisor's plain line inspection boundary stopped before the points were reached, whereas the track patrol incorporated the points. In undertaking a track patrol and supervisory plain line inspection simultaneously, the supervisor should take account of the differences in boundaries.
"On 18 February 2007, this difference was not accommodated in the substitution, and as a result the Lambrigg crossovers were not inspected on this date," it reads.
Had he continued to Lambrigg 2B, he would have found the third, and possibly second stretcher bars broken.
The RAIB also found by analysis that the stretcher bars had broken by load, not fatigue.
They agree with the Rail Industry report, that all stretcher bars were missing by the time the 17:15 from Euston passed the points, but disagree on the mechanism of derailment.
The RAIB say the train's wheels rode the rail, derailing the train, while the Rail Industry report claims the train's wheels struck the loose rail, causing the derailment.
In June, the RAIB issued urgent safety advice, calling for Network Rail to quickly examine all similar points where the line speed is 80mph or more.
120 sets of points were checked, and, "In six cases it was necessary to impose a 20 mph (32 km/h) speed restriction until faults to the track gauge, free wheel clearance and stretcher bars were rectified."
When the RAIB's final report is released, it will determine whether criminal action will be taken against any party or parties.