Cant say Im suprised! They clearly had no intention of keeping that rate as its too unrealistic, given ECB is 1.50% and they were paying 5% (excluding the bonus), when something looks to be too good to be true, its usually because it is!
Its not really a good account either, it can only be used on line, you get no interest paid in a month you make a withdrawal, and it is a variable rate, so all they were doing is putting out a fat rate to reel everybody in and then drop it!
Anyone with a lump sum in these accounts would be better locking it away if they dont need it, al least you will get a decent return with the various offers out there.