Barclays and RBS share prices fell by 25% and 17% respectively today; Barclays from £1.30 to £0.98 and RBS from £0.418 to £0.347.
My wife indicated that the deeper plunge at Barclays was due to my departure from the group on Wednesday. She said that once the markets got hold of the news there was clearly panic, but I believe that might only be part of the reason. (Just kidding).
The rationale behind the fall is reported as speculation about more toxic assets.
However, I believe the recent lift in the ban on short selling is more likely the reason behind the fall as speculators look for some new action. Expect the price to track back up next week as speculators close out their positions.