Rare footage of the previous record flooding in 1947.
This was caused by massive sudden snow melt - that's right, amazing as it may seem the previous winter had snowed, and snowed, and stayed cold and the snow had NOT melted, esp up in Wales, where the Severn headwaters rise.
Suddenly it warmed up and the river had, in effect, an entire winter's rain fall dumped into in in a matter of a few days.