A signal passed at danger is always a serious matter, and the Rail Accident Investigation Branch is treating an incident earlier this month at Doncaster in just such terms. Two freight trains became rather more dynamically coupled than would be desired on the morning of 7 July, damaging one locomotive, several intermodal wagons, and infrastructure at the site near Loversall Carr, a complex junction connecting the East Coast Main Line with freight lines, the nearby iPort rail terminal and mixed traffic lines to Gainsborough and several east coast ports.