My (then) 17 year old son was involved in an accident while leaving the M6 for the M5. Essentially, as he was moving left, he hit another car which was driving on the hard shoulder. At the time the other driver admitted responsibility, but of course this changed. My son's insurer contacted him months later asking if he would be willing to accept joint responsibility, which he agreed to. Now, nearly a year after the incident, they are asking if he will accept full responsibility, as the other insurers are contesting it. There were no witnesses, and no footage of the incident. His insurance is up for renewal, and his insurers are basing his quote on his being at fault (he did accept joint responsibility). My question is, when getting quotes from other companies, does he need to put down that he was at fault, or not?