They are too damn clever. Some years ago when I worked in London, I was running down the platform at Marble Arch to get to the carriage that had doors opposite the exit at my destination. I was wearing a bag with a shoulder strap and a flap that covered the whole side of the bag and buckled right underneath.
I was suddenly aware of someone running behind me and quite close so I looked over my shoulder and, sure enough, there was a young man there and when I looked at him he distanced himself and got into the immediate carriage. When I reached my carriage, I sat down, looked at my bag and discovered that the buckle under the bag was unbuckled.
Now I knew with absolute certainty that when I started my run down the platform the bag was fully buckled, buckle pin in the strap and loose end through the further bar of the buckle. Nothing was stolen, I saw him in time, and anyway the book I read on the British Rail train was at the top of the bag, which was why I knew the bag was buckled, I remembered putting the book away and fully buckling the bag.