I am executor and sole beneficiary of a deceased estate. I received a receipt as executor of will from a claimant written in their own handwriting with a supposed signature of deceased on it. The sale or contract for a vehicle supposedly took place 3 years ago. They claim they paid in full but never collected as the contract was conditional to work being carried out to the vehicle. This was never done by deceased and the vehicle was never handed over during deceased's life. The estate is verging on being impecunious and I am being sued for an amount that is now far more than the original sale price. They claim vehicle has gone up in value. There is a secured creditor and funeral expenses which leaves little to fight this case. I really need to sell car to clear funds for funeral expenses etc. The deceased did have a mental illness and I feel the claim is fraudulent. I need to know how I can prove this as the receipt seems to hold a lot of weight in terms of legitimizing the claim.