This is the ABS - Avocet High Security Cylinder Lock. It's unique design makes it tamper-proof.
If the cylinder is "snapped" then the burglar cannot get anywhere near the cam that operates the door bolt!
It's appearance alone is a huge deterrent to any thief and they will just move on until they find an easier "target". (In the unlikely event somebody should damage this lock, it can still be operated from inside your house so that you can still use the door while your waiting to replace it).
Even the keyway design prevents any conventional key entering it...so it cannot be "bumped" or picked.
These little beauties are highly recommended by police and insurance companies.