You'll only be responsible for it from the date of transfer so assuming you SORN or tax it as soon as you officially become the keeper you'll be fine. It will prompt them that the car still exists though and if it's not been SORNed properly in the past then they will go chasing after the previous keeper.

We've seen something similar with a couple of guys in a local club where one sold a car to another who SORNed it and suddenly the first guy gets paperwork through telling him he's going to be fined.

Iain