As mentioned earlier, your disclosure will show you everything that the crown will against you. Remember that there are more ways to get out of this than to go down for it, such as; a stay, creating reasonable doubt, the officer not showing up to trial and simply creating a strong case explaining the impossibility of the circumstances.

Remember, if you accept a lesser fine from the crown, you are saying that you're guilty of something.

From start to finish, maintain an attitude of innocence!

Good luck

It seems to me like you are guilty of your charge. But it all comes down to creating reasonable doubt when you present your case in court. Furthermore, you might get lucky and the officer not even show up, resulting in your charges being dropped. That's if you're lucky, so be prepaired with a series of questions to ask the officer which will cast doubt on your charge. Reasonable doubt is all you need, so you have the advantage.