This may not be something that has kept you awake of nights. I don’t need anything to keep me awake, so I was speculating idly on this topic while waiting for Morpheus to put in a welcome appearance.

Things started when I watched the film Riddick. This is a spectacularly inept sci-fi aliens vs humans movie. However, it does star Vin Diesel, and I rather like him. He’s a bit like Jean-Claude van Damme, or Arnie. No acting talent to speak of but entertaining enough when armed to the teeth and blowing things up. What you see is what you get.

For reasons I won’t go into, Riddick is stranded and left for dead on a scorching hot planet, and comes under alien attack, obviously. His distress beacon summons two ships, one loaded to the gunnels with heavily armed mercenaries, and one captained by a man from Riddick’s past. Yes, it’s that sort of film.

To take my mind off the terrible backdrop scenery (clearly not enough cash for CGI), I was looking at the finer details of the body armour the mercenaries were wearing. The basic design is one you’re familiar with, with overlapping plates arranged vertically to allow for movement. But here’s the thing. The bottom section of one plate overlaps the top section of the next plate. All fine and dandy. Or is it?

Say somebody is coming at you with a knife or a sword, and is intent on eviscerating you. Now unlike the traditional overhead stabbing beloved of Victorian melodramas, your experienced shiv artist is going to strike upwards. With the plates as traditionally overlaying, the blade will tend to go between them, won’t it? More logical to align the plates so the top edge of the lower one overlaps the bottom edge of the next one up. The blade will be much more likely to be deflected away from your vitals.

This has been a public service announcement.