Bellman
I would advise that you seek proper legal advice, I am not a lawyer and cannot advise you.
See
pepipoo and it's forums where various legally qualified people may be found.
From my limited experience this sounds like a very tricky and most unfortunate position for you and I am sorry to hear it. I assume from your post that you were absolutely not driving the car.
It brings up (again) many points about the whole 'fairness' or lack thereof of the whole system.
First, what details are there on the docs, was this a static gastso type camera or from an LTI (Cameravan) - ask if you are not sure. More evidence maybe available to you to view - like the second photo or video evidence. Often you have to insist before they provide it.
You need to establish that on the day on question, where were you, might you have been with anyone else that can verify your whereabouts, might a phone bill (mobile or landline) show that you were on the phone and who with ? Mobile phones can be traced to show the local cell that functioned, but I am not 100% certain if this at all traceable after the event, ask your provider. I know it to be true during a 999 call however.
If you cannot prove an alternative location for yourself at that very moment in time can you show anything either side of that time frame to show that perhaps your
known location makes it impossible to be elsewhere. ... and so on...
Usually a rear facing photo can show the height of a person driving - although not conclusive perhaps for a Court you maybe able to debate this point with the ex and so - e.g. not you etc.
Most cars do have 2 sets of keys, so where is the 2nd set ? Do you still have any involvement with the car in any way at all. Even told the garage to no longer send you the bills ?
I would have thought that a letter stating that you have parted company, you have nothing more to do with her, or her car (unless it is still yours in any way), you may need to keep saying this too, but I am somewhat concerned that they are now planning to take you to trial - on what basis ? The fact that she has named you means that you now are left proving that she holds a 'grudge' perhaps etc. and you face the Court? I don't suppose you know where the ex was on that day?
I would take legal advice on this because it is not in the best community interest to take a person to Court who was not driving. Can you show that you have no insurance for it ? Anything to help your case that you have cut the ties with her and so the car ? If you can show any of this attach it to the letter. Never state anything that you don't want the Court to be aware of.
You have 28 days to respond to their form so at this stage I'd send the letter / attachments and wait for a week and if nothing arrives then I'd call them. But I would start by contacting a lawyer before doing anything, and see if they might send a letter as this will carry more 'weight' to your message, plus if this gets nasty then a Lawyer has been involved from the start.
I cannot see that they can really prosecute you for failing to provide details, as this is the first that you have heard about it too. It might be that a Court will have to decide however. I am unclear how the 'ex' has been believed over you at this point.