There is a statutory defence if you can't identify the driver "using reasonable diligence", but it's a very tough sell. It's certainly not as simple as "Well it

There is a statutory defence if you can't identify the driver "using reasonable diligence", but it's a very tough sell. It's certainly not as simple as "Well it could have been me or my wife, but neither of us can remember which." - you'd have to be able to demonstrate what attempts you had made to identify the driver and why these had all been unsuccessful. You are expected to know who is driving your car at a given time. There was a case which was successfully defended, where the defendant asserted that the "reasonable diligence" requirement only applied after the request was received, and that there was no such requirement for you to retrospectively exercise such diligence. In other words, you must do everything you can to find out who was driving when you receive the notice, but that doesn't mean you have an obligation to keep records of who was driving in anticipation of such a request.