The Rail Accident Investigation Branch (RAIB) released its report on 18 August 2006 into the cutting of a rail from a line that was still open to traffic, near Thirsk station, on the East Coast Main Line on 11 January 2006.
The full report is available here:
A summary of the key points from the report are:-
On Wednesday 11 January 2006 a gang of track workers started to remove a rail on the line just north of Thirsk station.  It was then discovered that the rail had been severed on a line that was still open to traffic, and that the worksite had been established outside of an engineering possession.

A range of causal factors and two contributory factors to this incident have been identified.

The RAIB has made eight recommendations as a result of its investigation:
• One recommendation to the RSSB to covering forms used during possessions
• Seven recommendations to Network Rail covering staff briefings, procedures and documentation.