@@ -70,31 +70,6 @@ class CompImageHeader(Header):
         ["ZIMAGE", "ZCMPTYPE", "ZMASKCMP", "ZQUANTIZ", "ZDITHER0"]
     )
     _indexed_compression_keywords = {"ZNAXIS", "ZTILE", "ZNAME", "ZVAL"}
-    # TODO: Once it place it should be possible to manage some of this through
-    # the schema system, but it's not quite ready for that yet.  Also it still
-    # makes more sense to change CompImageHDU to subclass ImageHDU :/
-
-    def __new__(cls, table_header, image_header=None):
-        # 2019-09-14 (MHvK): No point wrapping anything if no image_header is
-        # given.  This happens if __getitem__ and copy are called - our super
-        # class will aim to initialize a new, possibly partially filled
-        # header, but we cannot usefully deal with that.
-        # TODO: the above suggests strongly we should *not* subclass from
-        # Header.  See also comment above about the need for reorganization.
-        if image_header is None:
-            return Header(table_header)
-        else:
-            return super().__new__(cls)
-
-    def __init__(self, table_header, image_header):
-        self._cards = image_header._cards
-        self._keyword_indices = image_header._keyword_indices
-        self._rvkc_indices = image_header._rvkc_indices
-        self._modified = image_header._modified
-        self._table_header = table_header
-
-    # We need to override and Header methods that can modify the header, and
-    # ensure that they sync with the underlying _table_header
 
     def __setitem__(self, key, value):
         # This isn't pretty, but if the `key` is either an int or a tuple we
@@ -119,38 +94,6 @@ def __setitem__(self, key, value):
 
         super().__setitem__(key, value)
 
-        if index is not None:
-            remapped_keyword = self._remap_keyword(keyword)
-            self._table_header[remapped_keyword, index] = value
-        # Else this will pass through to ._update
-
-    def __delitem__(self, key):
-        if isinstance(key, slice) or self._haswildcard(key):
-            # If given a slice pass that on to the superclass and bail out
-            # early; we only want to make updates to _table_header when given
-            # a key specifying a single keyword
-            return super().__delitem__(key)
-
-        if isinstance(key, int):
-            keyword, index = self._keyword_from_index(key)
-        elif isinstance(key, tuple):
-            keyword, index = key
-        else:
-            keyword, index = key, None
-
-        if key not in self:
-            raise KeyError(f"Keyword {key!r} not found.")
-
-        super().__delitem__(key)
-
-        remapped_keyword = self._remap_keyword(keyword)
-
-        if remapped_keyword in self._table_header:
-            if index is not None:
-                del self._table_header[(remapped_keyword, index)]
-            else:
-                del self._table_header[remapped_keyword]
-
     def append(self, card=None, useblanks=True, bottom=False, end=False):
         # This logic unfortunately needs to be duplicated from the base class
         # in order to determine the keyword
@@ -163,32 +106,14 @@ def append(self, card=None, useblanks=True, bottom=False, end=False):
         elif not isinstance(card, Card):
             raise ValueError(
                 "The value appended to a Header must be either a keyword or "
-                f"(keyword, value, [comment]) tuple; got: {card!r}"
+                "(keyword, value, [comment]) tuple; got: {!r}".format(card)
             )
 
         if self._is_reserved_keyword(card.keyword):
             return
 
         super().append(card=card, useblanks=useblanks, bottom=bottom, end=end)
 
-        remapped_keyword = self._remap_keyword(card.keyword)
-
-        # card.keyword strips the HIERARCH if present so this must be added
-        # back to avoid a warning.
-        if str(card).startswith("HIERARCH ") and not remapped_keyword.startswith(
-            "HIERARCH "
-        ):
-            remapped_keyword = "HIERARCH " + remapped_keyword
-
-        card = Card(remapped_keyword, card.value, card.comment)
-
-        # Here we disable the use of blank cards, because the call above to
-        # Header.append may have already deleted a blank card in the table
-        # header, thanks to inheritance: Header.append calls 'del self[-1]'
-        # to delete a blank card, which calls CompImageHeader.__deltitem__,
-        # which deletes the blank card both in the image and the table headers!
-        self._table_header.append(card=card, useblanks=False, bottom=bottom, end=end)
-
     def insert(self, key, card, useblanks=True, after=False):
         if isinstance(key, int):
             # Determine condition to pass through to append
@@ -209,33 +134,14 @@ def insert(self, key, card, useblanks=True, after=False):
         elif not isinstance(card, Card):
             raise ValueError(
                 "The value inserted into a Header must be either a keyword or "
-                f"(keyword, value, [comment]) tuple; got: {card!r}"
+                "(keyword, value, [comment]) tuple; got: {!r}".format(card)
             )
 
         if self._is_reserved_keyword(card.keyword):
             return
 
-        # Now the tricky part is to determine where to insert in the table
-        # header.  If given a numerical index we need to map that to the
-        # corresponding index in the table header.  Although rare, there may be
-        # cases where there is no mapping in which case we just try the same
-        # index
-        # NOTE: It is crucial that remapped_index in particular is figured out
-        # before the image header is modified
-        remapped_index = self._remap_index(key)
-        remapped_keyword = self._remap_keyword(card.keyword)
-
         super().insert(key, card, useblanks=useblanks, after=after)
 
-        card = Card(remapped_keyword, card.value, card.comment)
-
-        # Here we disable the use of blank cards, because the call above to
-        # Header.insert may have already deleted a blank card in the table
-        # header, thanks to inheritance: Header.insert calls 'del self[-1]'
-        # to delete a blank card, which calls CompImageHeader.__delitem__,
-        # which deletes the blank card both in the image and the table headers!
-        self._table_header.insert(remapped_index, card, useblanks=False, after=after)
-
     def _update(self, card):
         keyword = card[0]
 
@@ -244,50 +150,12 @@ def _update(self, card):
 
         super()._update(card)
 
-        if keyword in Card._commentary_keywords:
-            # Otherwise this will result in a duplicate insertion
-            return
-
-        remapped_keyword = self._remap_keyword(keyword)
-        self._table_header._update((remapped_keyword,) + card[1:])
-
-    # Last piece needed (I think) for synchronizing with the real header
-    # This one is tricky since _relativeinsert calls insert
-    def _relativeinsert(self, card, before=None, after=None, replace=False):
-        keyword = card[0]
-
-        if self._is_reserved_keyword(keyword):
-            return
-
-        # Now we have to figure out how to remap 'before' and 'after'
-        if before is None:
-            if isinstance(after, int):
-                remapped_after = self._remap_index(after)
-            else:
-                remapped_after = self._remap_keyword(after)
-            remapped_before = None
-        else:
-            if isinstance(before, int):
-                remapped_before = self._remap_index(before)
-            else:
-                remapped_before = self._remap_keyword(before)
-            remapped_after = None
-
-        super()._relativeinsert(card, before=before, after=after, replace=replace)
-
-        remapped_keyword = self._remap_keyword(keyword)
-
-        card = Card(remapped_keyword, card[1], card[2])
-        self._table_header._relativeinsert(
-            card, before=remapped_before, after=remapped_after, replace=replace
-        )
-
     @classmethod
     def _is_reserved_keyword(cls, keyword, warn=True):
         msg = (
-            f"Keyword {keyword!r} is reserved for use by the FITS Tiled Image "
+            "Keyword {!r} is reserved for use by the FITS Tiled Image "
             "Convention and will not be stored in the header for the "
-            "image being compressed."
+            "image being compressed.".format(keyword)
         )
 
         if keyword == "TFIELDS":
@@ -318,51 +186,6 @@ def _is_reserved_keyword(cls, keyword, warn=True):
 
         return False
 
-    @classmethod
-    def _remap_keyword(cls, keyword):
-        # Given a keyword that one might set on an image, remap that keyword to
-        # the name used for it in the COMPRESSED HDU header
-        # This is mostly just a lookup in _keyword_remaps, but needs handling
-        # for NAXISn keywords
-
-        is_naxisn = False
-        if keyword[:5] == "NAXIS":
-            with suppress(ValueError):
-                index = int(keyword[5:])
-                is_naxisn = index > 0
-
-        if is_naxisn:
-            return f"ZNAXIS{index}"
-
-        # If the keyword does not need to be remapped then just return the
-        # original keyword
-        return cls._keyword_remaps.get(keyword, keyword)
-
-    def _remap_index(self, idx):
-        # Given an integer index into this header, map that to the index in the
-        # table header for the same card.  If the card doesn't exist in the
-        # table header (generally should *not* be the case) this will just
-        # return the same index
-        # This *does* also accept a keyword or (keyword, repeat) tuple and
-        # obtains the associated numerical index with self._cardindex
-        if not isinstance(idx, int):
-            idx = self._cardindex(idx)
-
-        keyword, repeat = self._keyword_from_index(idx)
-        remapped_insert_keyword = self._remap_keyword(keyword)
-
-        with suppress(IndexError, KeyError):
-            idx = self._table_header._cardindex((remapped_insert_keyword, repeat))
-
-        return idx
-
-    def clear(self):
-        """
-        Remove all cards from the header.
-        """
-        self._table_header.clear()
-        super().clear()
-
 
 def _bintable_header_to_image_header(bintable_header):
     # Start with a copy of the table header.