if your mate had the small green bit of the log book and not the full log book the post office would not have taken the full log book,their procedure is to take a full logbook thats not in the person taxing the car's name and address.

next time just send your mate in with buisness insurance and the green bit and mot if applicable and kep fucking shtum if the postie asks if you just bought it and say yeah.

them green bits can be tippexed over and used again legally and i have done this so i know it works!!!!!!!!!!!!!!!!!!!!!