No, especially if it was local and at a weekend. I had the same situation, and only by the time on a shopping receipt could we work it out, if I had not kept the receipt I would not have been able to know for sure which of us it was. It was her by the way.
good advice can be found here http://forums.pepipoo.com/index.php?showforum=5
A few years ago now, but a fairly senior Police Officer used the defence that neither he or his wife could be sure who was driving, and so neither party was given a fine or points. If you get things reset to the point...