The coroner may be able to establish that the death was due to natural causes and that there is a doctor who is able to issue a Medical Certificate of Cause of Death. If this is the case then you will need to attend the Register Office to register the death.
If the Coroner is unable to do so then he will arrange for the deceased to be taken to the local hospital where, as required by law, a post-mortem examination will be performed (you do not have to use the Funeral Director who acts for the Coroner to carry out the funeral arrangements) This examination often shows that the death was due to natural causes and in such cases no inquest is required. The Coroner will inform you when he issues a document to allow you to attend a Register Office to register the death.
If the Coroner establishes the death was not due to natural causes then he is obliged to hold an inquest.