You can only do anything with the consent of the owner. You would either have to get them to agree to getting rid of it, or prove they are not of "sound mind" and were not of a state to have agreed to the contract in the first place. Contact the lease company and advise the vehicle has been mis-sold due to this. They should be concerned enough to cancel the agreement. I fully understand the predicament you are in. You need to speak to a solicitor to empower you to handle your relatives affairs and authorise you as your relative's appointed representative. You can also raise a complaint with the Finance Company, then the FOS (ombudsman).