Cheques in deceased name

My father has received cheques in my mothers name who passed away 3 years ago. However he has tried to deposit them to his own account with a death cert as proof and was told he could not deposit them.
Does anyone know what the policy is regarding this?

it is part of her estate and could be lodged into a solicitors account or executors account, if the payment can legally be made. some cheques, such as prize bonds cannot be cashed if payee is dead.

If your father contacts the payor and informs them of his wife's death they may advise him of the procedure i.e. whether they require death cert,copy of the will,claim form etc