Ex wife has car, log book in my name (UK resident), can I ask for the car back?

"A registration document (V5) is not proof of ownership"...If you have proof of who paid for the car then that person would be the legal owner of the car.

There is no "notice period" applicable to this because there is no case. The name on the V5C document (log book) is only that of the Registered Keeper (not "registered owner"). This is the person who is legally responsible for the roadworthiness of the car and to whom all penalty notices will be sent if they're not handed directly to the driver. The legal owner is the person who has "title" to the car. This is the person who has the receipt or other proof of sale in their name. Without this your friend has no chance of getting the car.

Firstly: remember that there is a difference between registered owner, and legal owner. Secondly: if the person can prove that they own the car: i.e. with receipts in their name, or credit debit card statements to that effect, then the ex-wife has no clear title to that car. Firstly: he should try and get the car back amicably. What i mean by that: is just simply ask for it. If that fails, then it's time to get the police involved, as they can go and act as a intermediary to get the car back. But that can only happen if he can prove beyond reasonable doubt that he owns the car.

As everyone says the keeper is not the owner. Who owns the car comes under your divorce settlement. What you can insist is she registers the car in her name and takes over the legal responsibility for it which you should do quickly unless the court awarded the car to you in the settlement.