There are many different ways of proving this type of offence. The least reliable is by way of an estimation, which is not much more than an educated guess. The police often use what is called a follow and time where they keep a constant distance from you and measure the speed of your vehicle against theirs. The most common is from a laser gun, radar or speed camera.
Commonly, we hear people claiming that they were not speeding despite an assertion to the contrary. We need to assess the evidence carefully. Cases involving the use of laser guns and/or speed cameras are complex indeed. The prosecution has many advantages and can tender certificates that are considered as proof of certain elements of the offence. Once again, you have to prove your innocence in a practical sense to rebut the presumptions in the certificates. Worse than that, you can be convicted of a speeding offence as an owner of a vehicle, even when it is known that you were not driving.
There are of course many serious traffic offences where speeding is an element and a mandatory loss of a driver's licence results. Usually, these periods are very lengthy and can have a significant impact on your life and others around you. Again, many of the periods cannot be reduced, but there are some circumstances that can result in the minimum penalties being reduced. It is important in these matters to seek legal advice.
In addition, payment of an expiation notice results in the attraction of demerit points. Often people tell us that they came to see us only when they were about to lose their licence. They often regret not challenging an earlier matter that in part contributed to their current disqualification.
We recommend that once you get an expiation notice or summons you seek legal advice in order to see if the matter can be challenged, or any loss of licence be avoided or reduced.