THE revelation that David Cameron paid off one private mortgage while he was billing the taxpayer for his constituency home in Witney could become the case that defines the principle over MPs’ expenses.

What has angered people during this whole scandal has been the huge greed by MPs as they have shovelled huge amounts of taxpayers’ money into paying for dry rot treatment in seaside holiday homes, pornos for the hubby, or maintenance on the moat.

Mr Cameron’s case does not have any of those flagrant abuses and so is a good one to ponder.

It comes down to whether or not the taxpayer should fund a second home in the constituency and, if so, whether the MP should then structure all of their other finances to lessen the burden on the public purse, even if it is ultimately to their financial detriment.