Rock armour was first used on the line "in a very small way" after floods in 2005, and more extensively last year when an embankment had to be reinstated. "The destructive problem with flooding is when water washes over the railway and runs down the other side," explains Hinshelwood. "If it keeps coming, it starts to accelerate, to scour and create turbulence, picking up ever-larger material the faster it washes across. You can't stop it, but rock armour slows it to a point where it doesn't wash ballast or embankment material away."