This prompts me to admit to a very serious mistake that I recently made on a flight back to "Blighty" on vacation.
My usual "carry-on bag" is my lap-top bag, and I had this in my posession for a 2-sector flight to UK. In addition to being baggage screened twice (by X-ray) at my airport of departure and again at the transit airport, I was somewhat concerned several days after my arrival in UK to find a "Stanley Knife" (aka Box Cutter?), bought a few weeks ago and forgotten, in one of the pockets of the lap-top bag
This was one of the"disposable" ones, so all plastic apart from the blade itself, and in a bag with a computer and lots of cables, power bricks and other "radar clutter", so I expect quite difficult to spot on X-ray, but certainly we are looking at a much more worrying hole in security than the pilot's wife or Cabin Crew's parent :o