Discuss your situation with the bank manager, who will ask to see a copy of the death certificate. Usually an interim death certificate is required until after the Coroner’s inquiry has ended.
When the bank becomes aware of a customer’s death, the bank account of the person who has died is usually frozen. This is required by law. The bank concerned will explain this to you, and how any funds can be released.
Banks cannot release funds, or allow an account to be operated, until probate of the will is granted or when Letters of Administration (which are necessary when someone has died intestate) have been obtained from the executor/s of the will. Your lawyer can help you in this.
If there is a joint bank account, where the account terms contain a survivorship clause, the surviving party may continue to operate the account as normal. In this case the bank usually suggests a new account be opened.