When I was in Australia I found two screwdrivers in my hand luggage that I had completely failed to remember were in there when I packaged and carefully took my swiss army card out of my wallet and swiss army knife out of my bag. Then on the way back at Heathrow the man discovered after much searching my old swiss army card that I though I had lost ages ago. It would have gone through scanners at Edinburgh, Healthrow and Sydney before they found it. Oops.