I have been caught like that before too. The guy said he would do the change of ownership on the way home and from the speeding fine I got a few months later I take it he didn't. I tried to contest the fine but got the story that well, whilst its under your name, you are liable for ALL fee's. So Dad and I had a chat about what to do and came to the conclusion that if the car was still registered under my name, then according to the police it was still mine.
A quick dig around and we found the spare key, went round to the guys house and drove the car back home. We gave him a few days and then rung him to ask how the car was going and we got a big, long sob story about how it had just been stolen. You should have heard the colourful langauge come from him when he heard that we had "stolen" the car.
A few hours later the police and him came around and had a bit of a chat with dad and myself and the police basically said to the guy that well, the car is registered under my name, no receipts were availible so according to them, it was my car and HE should be the one getting prosecuted. After we let him simmer down, I gave him the speeding fine and said that when that gets paid and the receipt for change of ownership was sighted by Dad and myself, he can get the car back. It took him a day but he can back with both receipts AND a personalised number plate

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Moral of the story, always keep your spare keys incase something goes wrong.
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