Part of the wall of an arch bridge and the footpath on top collapsed and a large volume of masonry fell onto the Midland Main Line at around 23.50 on 1 August. At the time of the collapse, drilling work was under way to investigate a depression in the footpath on the south side of the bridge. The bridge was closed to the public, but the railway lines below were open to traffic. There were a number of existing defects in the bridge structure which Network Rail had been monitoring for some years.

Drilling was being carried out to extract soil samples for analysis; shortly after work began, cracks appeared in the footpath, and then the adjacent wall, footpath and the drilling rig fell onto the railway. No-one was injured.

There were no trains in the immediate vicinity at the time. However, an empty train had passed less than five minutes before and a passenger service had gone by less than 10 minutes earlier. Rail services through the bridge were suspended until Wednesday 3 August to allow the bridge to be made safe.

The RAIB's investigation will examine the sequence of events leading up to partial collapse of the bridge, the construction and maintenance of the bridge, its recent history, arrangements for protection of the railway during the works and any relevant management issues.