Since we've lived here that have been several large rock and cliff falls, and unless I've misjudged this one, it isn't one of the biggest in that time. I'm not sure what the overall rate of retreat of the cliffs is, but if we are seeing a rise in sea levels and an increase in the number and intensity of storms it doesn't seem unreasonable to believe that we will see an increase in the rate of erosion.
The report I read said that several tonnes of rocks broke away, and it also says that a "Huge" section of the cliff fell into the sea. Solid Chalk has a density of around 2.5 gm/cc, so just a cubic metre weighs 2.5 tonnes. A massive fall would weigh quite a few tonnes, but I haven't been along with my tape measure to try to estimate the real size of the fall.