I would have thought No.10 was a bit feeble - what about the general who invaded Argentina without permission 200 or so years ago? And lots of expensive bridge disasters, the one in Oz that crashed, the Verazzano Narrows bridge in NY, the Tay rail bridge in Scotland, even the wobbly Millennium bridge. And how about the budgeting for the Dome or the upcoming Olympics? Oh and the capsizing of HMS Captain. And Cane Toads. And the Greek army that marched all the way to Persia only to find out it wasn't wanted (see Xenophon's Anabasis). And Cambyses mislaying an entire army in the Egyptian desert that hasn't been seen since. And Caesar adopting Brutus. And whoever suggested Quintilius Varus to go and duff up Arminius in the Teutoberger Wald which cost Augustus three legions and their standards. One could say that history is just us lurching from one ballsup to another, leaving a litter of 'good ideas' in our wake.