I want my camper back.

Our son took off to Glastonbury yesterday in our camper and left us his X Type Jaguar with a tank full of petrol. We've clocked up 95 miles so far and a third of the fuel is gone, I'm guessing that's around 18 or 19 miles to the gallon, or should that be gallons to the mile? we're walking for the rest of the week. He rang to say how grateful he was for the loan of the van as it's got everything he needs. So I told him that's OK and by the way, I've modified the Jag a bit by taking out the passenger seat and fitting a woodburner. He was a little concerned that I may have spoiled it's sleek lines by cutting a hole in the roof for the flue pipe, but was somewhat reassured when I said that I'd just smashed the side window and gone through there. Anyway, roll on next Monday when we can swap back, kids today have more money than sense.