In July 2025, the Rail Accident Investigation Branch launched an investigation into the derailment at Denbigh Hall South Junction, near Bletchley, Buckinghamshire.

The incident occurred on the 26th June, around 12:27, when an out-of-service train was travelling at 15 mph when it derailed at the junction.

RAIB have now released their report with recommendations.

They investigated the underlying factor of variable knowledge of diamond points and relevant training for signallers when applying the Rule Book modules for authorising trains for wrong direction movements.

They observed that the Rule Book did not cover the circumstances of this specific wrong-direction movement.

They have made the following recommendations, one addressing Network Rail to provide training for signallers so that tools and techniques can be used for proposing paths.

Two recommendations go to both Network Rail and West Midlands Trains, who should develop training for diamond points.

Lastly, the Rail Safety and Standards Board were given a recommendation to consider whether the Rule Book should account for scenarios such as this, where the signal is located near the start of a planned wrong direction movement.