diff --git a/changelog.d/6858.misc b/changelog.d/6858.misc
new file mode 100644
index 0000000000..08aa80bcd9
--- /dev/null
+++ b/changelog.d/6858.misc
@@ -0,0 +1 @@
+Refactoring work in preparation for changing the event redaction algorithm.
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 89d41d82b6..a842661a90 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -16,12 +16,13 @@
 
 import os
 from distutils.util import strtobool
+from typing import Optional, Type
 
 import six
 
 from unpaddedbase64 import encode_base64
 
-from synapse.api.room_versions import EventFormatVersions
+from synapse.api.room_versions import EventFormatVersions, RoomVersion, RoomVersions
 from synapse.types import JsonDict
 from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
@@ -407,7 +408,7 @@ class FrozenEventV3(FrozenEventV2):
         return self._event_id
 
 
-def event_type_from_format_version(format_version):
+def event_type_from_format_version(format_version: int) -> Type[EventBase]:
     """Returns the python type to use to construct an Event object for the
     given event format version.
 
@@ -427,3 +428,14 @@ def event_type_from_format_version(format_version):
         return FrozenEventV3
     else:
         raise Exception("No event format %r" % (format_version,))
+
+
+def make_event_from_dict(
+    event_dict: JsonDict,
+    room_version: RoomVersion = RoomVersions.V1,
+    internal_metadata_dict: JsonDict = {},
+    rejected_reason: Optional[str] = None,
+) -> EventBase:
+    """Construct an EventBase from the given event dict"""
+    event_type = event_type_from_format_version(room_version.event_format)
+    return event_type(event_dict, internal_metadata_dict, rejected_reason)
diff --git a/synapse/events/builder.py b/synapse/events/builder.py
index 8d63ad6dc3..a0c4a40c27 100644
--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -28,11 +28,7 @@ from synapse.api.room_versions import (
     RoomVersion,
 )
 from synapse.crypto.event_signing import add_hashes_and_signatures
-from synapse.events import (
-    EventBase,
-    _EventInternalMetadata,
-    event_type_from_format_version,
-)
+from synapse.events import EventBase, _EventInternalMetadata, make_event_from_dict
 from synapse.types import EventID, JsonDict
 from synapse.util import Clock
 from synapse.util.stringutils import random_string
@@ -256,8 +252,8 @@ def create_local_event_from_event_dict(
     event_dict.setdefault("signatures", {})
 
     add_hashes_and_signatures(room_version, event_dict, hostname, signing_key)
-    return event_type_from_format_version(format_version)(
-        event_dict, internal_metadata_dict=internal_metadata_dict
+    return make_event_from_dict(
+        event_dict, room_version, internal_metadata_dict=internal_metadata_dict
     )
 
 
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index ebe8b8e9fe..eea64c1c9f 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -29,7 +29,7 @@ from synapse.api.room_versions import (
     RoomVersion,
 )
 from synapse.crypto.event_signing import check_event_content_hash
-from synapse.events import EventBase, event_type_from_format_version
+from synapse.events import EventBase, make_event_from_dict
 from synapse.events.utils import prune_event
 from synapse.http.servlet import assert_params_in_dict
 from synapse.logging.context import (
@@ -374,8 +374,7 @@ def event_from_pdu_json(
     elif depth > MAX_DEPTH:
         raise SynapseError(400, "Depth too large", Codes.BAD_JSON)
 
-    event = event_type_from_format_version(room_version.event_format)(pdu_json)
-
+    event = make_event_from_dict(pdu_json, room_version)
     event.internal_metadata.outlier = outlier
 
     return event
diff --git a/tests/api/test_filtering.py b/tests/api/test_filtering.py
index 63d8633582..4e67503cf0 100644
--- a/tests/api/test_filtering.py
+++ b/tests/api/test_filtering.py
@@ -25,7 +25,7 @@ from twisted.internet import defer
 from synapse.api.constants import EventContentFields
 from synapse.api.errors import SynapseError
 from synapse.api.filtering import Filter
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 
 from tests import unittest
 from tests.utils import DeferredMockCallable, MockHttpResource, setup_test_homeserver
@@ -38,7 +38,7 @@ def MockEvent(**kwargs):
         kwargs["event_id"] = "fake_event_id"
     if "type" not in kwargs:
         kwargs["type"] = "fake_type"
-    return FrozenEvent(kwargs)
+    return make_event_from_dict(kwargs)
 
 
 class FilteringTestCase(unittest.TestCase):
diff --git a/tests/crypto/test_event_signing.py b/tests/crypto/test_event_signing.py
index 6143a50ab2..62f639a18d 100644
--- a/tests/crypto/test_event_signing.py
+++ b/tests/crypto/test_event_signing.py
@@ -19,7 +19,7 @@ from unpaddedbase64 import decode_base64
 
 from synapse.api.room_versions import RoomVersions
 from synapse.crypto.event_signing import add_hashes_and_signatures
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 
 from tests import unittest
 
@@ -54,7 +54,7 @@ class EventSigningTestCase(unittest.TestCase):
             RoomVersions.V1, event_dict, HOSTNAME, self.signing_key
         )
 
-        event = FrozenEvent(event_dict)
+        event = make_event_from_dict(event_dict)
 
         self.assertTrue(hasattr(event, "hashes"))
         self.assertIn("sha256", event.hashes)
@@ -88,7 +88,7 @@ class EventSigningTestCase(unittest.TestCase):
             RoomVersions.V1, event_dict, HOSTNAME, self.signing_key
         )
 
-        event = FrozenEvent(event_dict)
+        event = make_event_from_dict(event_dict)
 
         self.assertTrue(hasattr(event, "hashes"))
         self.assertIn("sha256", event.hashes)
diff --git a/tests/events/test_utils.py b/tests/events/test_utils.py
index 2b13980dfd..45d55b9e94 100644
--- a/tests/events/test_utils.py
+++ b/tests/events/test_utils.py
@@ -13,8 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 from synapse.events.utils import (
     copy_power_levels_contents,
     prune_event,
@@ -30,7 +29,7 @@ def MockEvent(**kwargs):
         kwargs["event_id"] = "fake_event_id"
     if "type" not in kwargs:
         kwargs["type"] = "fake_type"
-    return FrozenEvent(kwargs)
+    return make_event_from_dict(kwargs)
 
 
 class PruneEventTestCase(unittest.TestCase):
@@ -38,7 +37,9 @@ class PruneEventTestCase(unittest.TestCase):
     `matchdict` when it is redacted. """
 
     def run_test(self, evdict, matchdict):
-        self.assertEquals(prune_event(FrozenEvent(evdict)).get_dict(), matchdict)
+        self.assertEquals(
+            prune_event(make_event_from_dict(evdict)).get_dict(), matchdict
+        )
 
     def test_minimal(self):
         self.run_test(
diff --git a/tests/federation/test_federation_server.py b/tests/federation/test_federation_server.py
index 1ec8c40901..e7d8699040 100644
--- a/tests/federation/test_federation_server.py
+++ b/tests/federation/test_federation_server.py
@@ -15,7 +15,7 @@
 # limitations under the License.
 import logging
 
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 from synapse.federation.federation_server import server_matches_acl_event
 from synapse.rest import admin
 from synapse.rest.client.v1 import login, room
@@ -105,7 +105,7 @@ class StateQueryTests(unittest.FederatingHomeserverTestCase):
 
 
 def _create_acl_event(content):
-    return FrozenEvent(
+    return make_event_from_dict(
         {
             "room_id": "!a:b",
             "event_id": "$a:b",
diff --git a/tests/replication/slave/storage/test_events.py b/tests/replication/slave/storage/test_events.py
index b1b037006d..d31210fbe4 100644
--- a/tests/replication/slave/storage/test_events.py
+++ b/tests/replication/slave/storage/test_events.py
@@ -15,7 +15,7 @@ import logging
 
 from canonicaljson import encode_canonical_json
 
-from synapse.events import FrozenEvent, _EventInternalMetadata
+from synapse.events import FrozenEvent, _EventInternalMetadata, make_event_from_dict
 from synapse.events.snapshot import EventContext
 from synapse.handlers.room import RoomEventSource
 from synapse.replication.slave.storage.events import SlavedEventStore
@@ -90,7 +90,9 @@ class SlavedEventStoreTestCase(BaseSlavedStoreTestCase):
         msg_dict["content"] = {}
         msg_dict["unsigned"]["redacted_by"] = redaction.event_id
         msg_dict["unsigned"]["redacted_because"] = redaction
-        redacted = FrozenEvent(msg_dict, msg.internal_metadata.get_dict())
+        redacted = make_event_from_dict(
+            msg_dict, internal_metadata_dict=msg.internal_metadata.get_dict()
+        )
         self.check("get_event", [msg.event_id], redacted)
 
     def test_backfilled_redactions(self):
@@ -110,7 +112,9 @@ class SlavedEventStoreTestCase(BaseSlavedStoreTestCase):
         msg_dict["content"] = {}
         msg_dict["unsigned"]["redacted_by"] = redaction.event_id
         msg_dict["unsigned"]["redacted_because"] = redaction
-        redacted = FrozenEvent(msg_dict, msg.internal_metadata.get_dict())
+        redacted = make_event_from_dict(
+            msg_dict, internal_metadata_dict=msg.internal_metadata.get_dict()
+        )
         self.check("get_event", [msg.event_id], redacted)
 
     def test_invites(self):
@@ -345,7 +349,7 @@ class SlavedEventStoreTestCase(BaseSlavedStoreTestCase):
         if redacts is not None:
             event_dict["redacts"] = redacts
 
-        event = FrozenEvent(event_dict, internal_metadata_dict=internal)
+        event = make_event_from_dict(event_dict, internal_metadata_dict=internal)
 
         self.event_id += 1
 
diff --git a/tests/state/test_v2.py b/tests/state/test_v2.py
index 0f341d3ac3..5bafad9f19 100644
--- a/tests/state/test_v2.py
+++ b/tests/state/test_v2.py
@@ -22,7 +22,7 @@ import attr
 from synapse.api.constants import EventTypes, JoinRules, Membership
 from synapse.api.room_versions import RoomVersions
 from synapse.event_auth import auth_types_for_event
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 from synapse.state.v2 import lexicographical_topological_sort, resolve_events_with_store
 from synapse.types import EventID
 
@@ -89,7 +89,7 @@ class FakeEvent(object):
         if self.state_key is not None:
             event_dict["state_key"] = self.state_key
 
-        return FrozenEvent(event_dict)
+        return make_event_from_dict(event_dict)
 
 
 # All graphs start with this set of events
diff --git a/tests/test_event_auth.py b/tests/test_event_auth.py
index ca20b085a2..bfa5d6f510 100644
--- a/tests/test_event_auth.py
+++ b/tests/test_event_auth.py
@@ -18,7 +18,7 @@ import unittest
 from synapse import event_auth
 from synapse.api.errors import AuthError
 from synapse.api.room_versions import RoomVersions
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 
 
 class EventAuthTestCase(unittest.TestCase):
@@ -94,7 +94,7 @@ TEST_ROOM_ID = "!test:room"
 
 
 def _create_event(user_id):
-    return FrozenEvent(
+    return make_event_from_dict(
         {
             "room_id": TEST_ROOM_ID,
             "event_id": _get_event_id(),
@@ -106,7 +106,7 @@ def _create_event(user_id):
 
 
 def _join_event(user_id):
-    return FrozenEvent(
+    return make_event_from_dict(
         {
             "room_id": TEST_ROOM_ID,
             "event_id": _get_event_id(),
@@ -119,7 +119,7 @@ def _join_event(user_id):
 
 
 def _power_levels_event(sender, content):
-    return FrozenEvent(
+    return make_event_from_dict(
         {
             "room_id": TEST_ROOM_ID,
             "event_id": _get_event_id(),
@@ -132,7 +132,7 @@ def _power_levels_event(sender, content):
 
 
 def _random_state_event(sender):
-    return FrozenEvent(
+    return make_event_from_dict(
         {
             "room_id": TEST_ROOM_ID,
             "event_id": _get_event_id(),
diff --git a/tests/test_federation.py b/tests/test_federation.py
index 68684460c6..9b5cf562f3 100644
--- a/tests/test_federation.py
+++ b/tests/test_federation.py
@@ -2,7 +2,7 @@ from mock import Mock
 
 from twisted.internet.defer import ensureDeferred, maybeDeferred, succeed
 
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 from synapse.logging.context import LoggingContext
 from synapse.types import Requester, UserID
 from synapse.util import Clock
@@ -43,7 +43,7 @@ class MessageAcceptTests(unittest.TestCase):
             )
         )[0]
 
-        join_event = FrozenEvent(
+        join_event = make_event_from_dict(
             {
                 "room_id": self.room_id,
                 "sender": "@baduser:test.serv",
@@ -105,7 +105,7 @@ class MessageAcceptTests(unittest.TestCase):
         )[0]
 
         # Now lie about an event
-        lying_event = FrozenEvent(
+        lying_event = make_event_from_dict(
             {
                 "room_id": self.room_id,
                 "sender": "@baduser:test.serv",
diff --git a/tests/test_state.py b/tests/test_state.py
index 1e4449fa1c..d1578fe581 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -20,7 +20,7 @@ from twisted.internet import defer
 from synapse.api.auth import Auth
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.room_versions import RoomVersions
-from synapse.events import FrozenEvent
+from synapse.events import make_event_from_dict
 from synapse.events.snapshot import EventContext
 from synapse.state import StateHandler, StateResolutionHandler
 
@@ -66,7 +66,7 @@ def create_event(
 
     d.update(kwargs)
 
-    event = FrozenEvent(d)
+    event = make_event_from_dict(d)
 
     return event