Autocomplete searches all address books, so the unwanted entry is probably in Collected Addresses.

Not true this time. I've searched ALL the addresses folders and it is NO where in the list.

Does the contact appear if you search All Address Books in Address Book? Or, if you search Config. editor in Options/General (at the bottom)?

As stated previously, I have thoroughly searched ALL (this means each and every) address book and the deleted address does not appear. I've attached a picture to show that when I begin typing the word "GERALD" in a new email address bar, it suggests two names. The last one showing has been deleted but still appears here. This means that each time I send Gerald an email, I must be VERY careful to choose the correct address.

I did look at your suggested Config editor and a search there brings up no email addresses.

OK, and I presume the live.com address is not listed as an Additional Email in the contact card for Gerald, which has the gmail address in the Email field. If the live.com address is not visible anywhere, it suggests it was deleted, but not actually removed from the underlying address book file. Prior to TB 78, you could open Personal Address Book (abook.mab in the profile folder) in a text editor to search for corrupted entries, but now the addresses are stored in sqlite files.

If the underlying address book is corrupted, there is a way to repair it, but it's best to first rule out obvious causes.