This idea is important because it is not right to presume guilt, or to fine first and ask questions later. I imagine vehicle offences are a tricky issue because it can be hard to track down the driver and get any money from them. This is probably why the keeper of the vehicle is presumed guilty and it is up to them to prove their innocence. However, this does not make it right. It goes against the principles of justice and is just a cheap and easy way to apportion blame and make sure a fine is paid.
Drivers or registered keepers of vehicles should not be presumed guilty after an alleged offence related to a vehicle. If they dispute the charges, they should not have to pay any money first and be forced to appeal in order to get their money back.
The person driving the vehicle is not necessarily the registered keeper or owner anyway, so if a vehicle is clamped or towed away, it is not right that the keeper should then have to pay a fee to be allowed their car back. This would remove any legitimate reason for clamping vehicles anyway, and vehicles should only ever be towed away if they are causing an obstruction that urgently needs unblocking.
Under this system, if a car is towed away, a fee can be requested at the time of retrieval, but payment at that time would not be compulsory. If the keeper refuses to pay, the case can then go to court and the driver of the car can be sued for the money, or the driver could pay at a later time. Compulsory payment first goes against the presumption of innocence. If the person driving is not the keeper, it should not be up to the keeper to pay up and get the money from the driver.
Vehicle offences (of any type) should relate to the driver at the time, not the keeper and there should be no presumption that it is the keeper that has committed an offence. The onus should be on the prosecutor to prove an offence had been committed and to prove who committed the offence.