So it's the same on both sides of the pond. I've found every time I'm prepared to fight a ticket, it's dropped. The cop is usually not interested in taking the time to testify. In other cases, it was a K55 radar unit, and when I ask for the daily calibration records, it's usually "uh, we left that in our other jacket. case dismissed"
I've been charged with running a toll booth, where the truck had the same tag number as my motorcycle - the photo was included with the mailed citation.
I was told "THAT'S NOT POSSIBLE" of course, and it was dropped when I presented all my evidence of vehicle registration, etc. I found out that the truck was from another state with a different numbering scheme.
Edit: I got the stern "you're lucky" from the judge and I responded with "No, your Honor, I just don't run toll booths... I'm not that poor." and gave the gimlet stare right back.
I've also been told if I fight a ticket the cop would add more offenses (which is "illegal duress against due process" as he's trying to keep me from showing up in court) so not only did I get my speeding ticket dropped, he got a black mark on his record.