The teeth part into a grin even wider than mine, I push the padlocked zip-pulls to one side, and my suitcase lies open, all my stuff accessible. But the case is now unusable, you're thinking? No way: all I have to do is pull on the padlock, and the zip fasteners do their usual business. The case looks and functions as normal.
And of course, that's a whole new problem suddenly revealed. Because if I can do it, so quickly and easily, so can anyone else with access to my bag on its solitary travels through any airport. They could take out — or, more sinisterly, put in — anything they want, and leave the bag looking untouched. That expensive padlock is mere decoration.
Again, whatcha gonna do? Here are some solutions.
• Plastic wrap: low-tech, but effective as a deterrent and pretty much standard if you're passing through Johannesburg. But of course you have to have it done each time, there's queuing involved, it costs about $15, and there's not much chance of all that plastic getting recycled. Add that to your carbon-credit guilt. Also, in the US the Transport Security Administration (TSA) people may well cut it off, even before your case has ended its journey.
• Duct tape over the zip. Even more low-tech, it looks dorky and will eventually leave a sticky residue, but it may be all that's needed to persuade the thief to pass on to more defenceless bag. But TSA people may remove it.
• Chain mail: looking as paranoid as tape, it's a sort of metal netting that you wrap around your bag, and could be a signal to the ill-intentioned that there's something especially valuable inside - the eternal conundrum. Also, it still needs padlock closure: TSA-approved if you're heading to or through the US. Google tells me helpfully that there are apparently only seven master keys for TSA locks, and you can view them on the internet, so determined baddies can make duplicates. If you're not US-bound, of course, you can use a regular padlock. Just be aware that combination locks, with enough time, aren't impregnable either. Someone once opened for me a 3-digit lock in less than half an hour, just by methodically working through the sequences (it was a long, boring bus trip).
• Suitcase straps for an extra layer of deterrent protection. Unfortunately, zips can still be opened for opportunistic groping; and the strap catches are also TSA-type - see above.
• Devices to lock the padlock to the handle, so it can't be slid along to close the zip again. Of course, the zip can be opened in the first place, leaving your remaining belongings to spill out.
• Suitcases with double-toothed zips that claim to be impregnable to ballpoint penetration: these are, naturally, expensive. And you'll still need TSA-approved locks if you're flying through the US. Bit of a theme developing here, isn't there?
• Hard-shell suitcases (generally more robust anyway) which don't have zips. Catches seem a bit retro, but they work perfectly well and are impervious to ballpoints. The inbuilt locks will, again, be TSA-type however, so one of those seven keys will still open it.
It is, at the very least, ironic that demands of the US Transport Security Administration result in less security for your luggage. Don't be tempted, however, to think that with all those bags swirling through US airports, your more secure non-TSA padlock won't be noticed. These guys are obsessive, and will blithely cut it off, leaving your case unprotected for the rest of its journey. Incidentally, they do open some locks to check suspicious contents: I've arrived home to find an unexpected little billet-doux inside my case from the inspectors.
There is no ultimate solution, it seems, other than packing your valuables in your carry-on bag and, for your check-in suitcase, using whichever deterrent you can afford and/or live with.
Then cross your fingers.