Cheque Issue

Hi Sir!Good Afternoon to all.Please suggest your valuable suggestions regarding this issue.One of my uncle gave a cheque to his friend for Rs.20 lakhs after that his friend told him that he had missed that cheque and with good concern my uncle deposited cash through bank in his account and after these many years in 2016 another person unknown to my uncle has sent a notice stating that he has to pay the amount of Rs.20 lakhs to him.My uncle is saying that the person has given the cheque to this person and claiming for money.my uncle has not written the total amount of rupees on the cheque.they themselves has written in words when we saw the writing on the cheque we understood that it was written by some other person and not by my uncle. when compared to the signature is there any chance that we can proceed further.please advise your valuable points how to over come this problem. Thank you sir Surendhar