Just got back from being away for a week and received a speeding ticket through the post, thing is, the letter is dated 5/4/07 and the said offence (38 in a 30) was commited on 3/12/06

Surely they cant expect me to remember who was driving 4 months ago!
The only sense i can make of it is that i bought the car around that time so i dug out the log book and actually found out it was the exact day of the offence 3/12/06
Im not saying that it wasn't me driving, it may well have been, but i definately do not remember being flashed at any time.
The letter asks if i was the driver at said time and date but only gives the options yes or no, i need a "dont know" option
Where do i stand with this?

Anyone been in a similar position?
Dunno what to put tbh.....