The pound has had its worst day since 1992 when it crashed out of the ERM. Why? Speculation and gambling by merchant banks mostly. Not that runs on the pound are exactly a new phenomonon.
If you look back to the 60's and 70's, currency speculation has brought the country low on numerous occasions. Typically speculation has occured during Labour governments, but 1992 it was John Major's Conservative government that got hammered; in fact it was only a short-term cash injection from the Sultan of Brunei that saved the country from bankruptcy. Today wasn't Black Friday, but it's part of an ongoing bet against the pound, and we may well get there yet.
As Joshua said in Wargames (a sci fi movie from 1983) "A strange game. The only winning move is not to play. How about a nice game of chess?"
