Which?
OK, maybe I'm missing the point here, but do Which? not test products and give the "low down" on those that work, those that don't, and those that are the Best Buy!
Would it not have made sense for them to test a rage of secure deletion software and then publish their findings.
As for breaking up the hard disk with a hammer - unless you destroy the patter, there are still companies that can retrieve data from the disk (yes, expensive, and would probably only be done by MI5, CIA, MOSAD, but it can be done). So the Which? advice to physically break up the disk is flawed