My son privately sold an elderly Daihatsu Sportrak through our local classifieds. The buyers explained they were unable to make the 40-mile journey to view it, but they said if he delivered it, they would pay the £750 asking price in cash without quibble. Despite some misgivings, we drove it to them and they duly paid as promised without even test driving it. They have now contacted him six weeks later to say that it has always run roughly and this has now been diagnosed as a burnt out valve which, they have been told, would not have happened overnight and would have been the case at the time of sale. Whilst the car was always a bit ‘agricultural’, he was not aware of this problem. As a result they are demanding my son pays £400 towards the £600 repair cost or takes the car back. He is sympathetic to the problem, but is he legally required to meet their demands?