I was interested to read in the MSM recently that the UK was fortunate in that it was "impossible" for us to be hit by a Tsunami like the one that recently devastated Japan.
between six to eight thousand years ago, Great Britain and the northern British Isles was inundated by a huge Tsunami which wiped out the coast of the North Sea.
Whereas most tsunamis are caused by undersea earth quakes, some are caused by undersea "landslides".
The North Sea tsunami was caused by a huge submarine landslide off the coast of Norway, and the area is now known geographically as the "Storegga Slide".
There were actually three major slides in the area, the first was around 50,000 years ago(BP), a second one around 22,000 BP, followed by one around 7300BP. This lasttsunami is estimated to have been between 19-25m high in the shetlands, and around 9m high along the coast of NE England.
Here is a computer simulated map of the extent of the slide, with the height of the average "run up" of the Tsunami- (as opposed to recorded peak heights due to wave focus, which were much higher in places such as river mouths etc)
T. Bugge, R. H. Belderson, N. H. Kenyon “The Storegga Slide” Philosophical Transactions of the Royal Society of London 1988