I did a lot of research to find a daypack/backpack for the hubby. It needed to be secure, comfortable, and able to hold raincoats, snacks and the inevitable purchases along the way.
This one met and exceeded all those requirements.
The security feature was tested while in Florence, Italy.
After being bumped while shopping (by a well dressed woman who quickly ran out of the store and disappeared into a huge crowd), we found that she was unsuccessful in unlatching the zipper. All contents were still secure.