I heard this problem once, someone bought a scrap car with a private plate on. got a mate to do an MOT , and applied to transfer it, got a letter back from DVLA saying since there was a break between tax running out and sorn declared, it had to be taxed, so forked out £101 for 6 months tax, and sent everythign back off again, a week or so later got an appointment through saying they wanted to inspect the donor vehicle!!! obviously couldnt do this as the car had already been crushed, so not wanting to loose the plate and transfer fee etc, repoted the car stolen. got the £80 transfer fee refunded, and got refund of duty on the tax. Had to wait 12 months to get the plate transfered, as DVLA rules state once a vehicle is stolen with a plate you have to either wait 12 months, or until the vehicle is recovered, whichever is the sooner before you can use the plate again.

Is a mess on, but better than loosing the plate.

Hyperthetically speaking of course