A report into the landslide which caused a train to derail near Watford Junction station says Network Rail failed to identify such a risk, despite a previous collision at the same location decades before.

Just before 7am on Friday September 16 last year, a London Midland train hit a landslip caused by torrential rain at the entrance to the Hunton Bridge tunnel, derailing one coach.

Shortly afterwards, the derailed carriage was struck by a passenger train travelling in the opposite direction.

Both trains were damaged but no passengers or crew were seriously injured.

A Rail Accident Investigation Branch report released today (Thursday) revealed that the site had not been identified by Network Rail as being at risk of a flooding-induced landslip.

This was despite a similar event occurring at the same spot in 1940, also causing a derailment.

The report said: “Drawings from the 1940s relating to a structure subsequently built to repair the slope were held in a Network Rail archive, but were not available to either Network Rail’s asset management team or the designers of a slope protection project, which was ongoing at this location at the time of the accident.

“As a consequence, this project made no provision for drainage.”

The report made six recommendations, four of them addressed to Network Rail, which include the improvement of drainage and the identification of locations vulnerable to washout.

In his conclusion, chief inspector Simon French added: “The landslip that caused the derailment occurred at a location that had not been identified as being at high risk.

“Extreme weather events may cause earthwork failures anywhere on the network, and existing methods of assessing risk may never be a totally reliable method of predicting when and where they will occur.

“This leads me to conclude that more needs to be done to ensure that the fundamental cause of so many earthwork failures – poor drainage – is properly addressed.”

The report also praised the swift reactions of the two drivers, which it said helped prevent a more tragic disaster from occurring.