Thanks folks
You can cut it with a blade, however it means you need to use several different tools to break the lock, and even then it's pretty hard!
Making a thief need several tools is definitely a good thing. If the two tools required were an angle grinder and a huge boltcutter then that would be great, but what you seem to have is some fabric that can be cut with a blade or scissors (not exactly hard to find) and a chain that can be cut moderately sized cutter (there's a reason chains of that size aren't recommended on the Locks that Work thread). Unless you've invented a new alloy that (8mm?) chain could well be cut with croppers.
Making a thief need several tools is definitely a good thing. If the two tools required were an angle grinder and a huge boltcutter then that would be great, but what you seem to have is some fabric that can be cut with a blade or scissors (not exactly hard to find) and a chain that can be cut moderately sized cutter (there's a reason chains of that size aren't recommended on the Locks that Work thread). Unless you've invented a new alloy that (8mm?) chain could well be cut with croppers.