It is blurred on our server before the photograph is stored. The unblurred original never reaches permanent storage — it exists in memory for as long as it takes to blur it. What is written to the bucket is the blurred image, and that is the only version that can ever be served.
If the plate on the first photograph is legible, it is read once before that: the registration is sent to the DVSA, which answers with the make, model, year, fuel and engine size, and the flow uses that instead of guessing the car from its shape. The registration is not sent back to your browser, not written to any row, and not put in a log. There is no column in the database that could hold one.
You can also type a registration yourself on the first screen, which does the same thing and is answered the same way.
The blur is automatic, so it is fallible. If you can see a plate that survived, delete the photograph and tell us.