diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index 4f9c3c9db8..9e912fdfbe 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -25,6 +25,7 @@ from synapse.api.errors import AuthError, Codes, SynapseError, EventSizeError
 from synapse.types import Requester, RoomID, UserID, EventID
 from synapse.util.logutils import log_function
 from synapse.util.logcontext import preserve_context_over_fn
+from synapse.util.metrics import Measure
 from unpaddedbase64 import decode_base64
 
 import logging
@@ -44,6 +45,7 @@ class Auth(object):
 
     def __init__(self, hs):
         self.hs = hs
+        self.clock = hs.get_clock()
         self.store = hs.get_datastore()
         self.state = hs.get_state_handler()
         self.TOKEN_NOT_FOUND_HTTP_STATUS = 401
@@ -66,9 +68,9 @@ class Auth(object):
         Returns:
             True if the auth checks pass.
         """
-        self.check_size_limits(event)
+        with Measure(self.clock, "auth.check"):
+            self.check_size_limits(event)
 
-        try:
             if not hasattr(event, "room_id"):
                 raise AuthError(500, "Event has no room_id: %s" % event)
             if auth_events is None:
@@ -127,13 +129,6 @@ class Auth(object):
                 self.check_redaction(event, auth_events)
 
             logger.debug("Allowing! %s", event)
-        except AuthError as e:
-            logger.info(
-                "Event auth check failed on event %s with msg: %s",
-                event, e.msg
-            )
-            logger.info("Denying! %s", event)
-            raise
 
     def check_size_limits(self, event):
         def too_big(field):
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index aaf6b1b837..13a675b208 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -316,7 +316,11 @@ class BaseHandler(object):
         if ratelimit:
             self.ratelimit(requester)
 
-        self.auth.check(event, auth_events=context.current_state)
+        try:
+            self.auth.check(event, auth_events=context.current_state)
+        except AuthError as err:
+            logger.warn("Denying new event %r because %s", event, err)
+            raise err
 
         yield self.maybe_kick_guest_users(event, context.current_state.values())
 
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 5ac55e10f3..d95e0b23b1 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -681,9 +681,13 @@ class FederationHandler(BaseHandler):
             "state_key": user_id,
         })
 
-        event, context = yield self._create_new_client_event(
-            builder=builder,
-        )
+        try:
+            event, context = yield self._create_new_client_event(
+                builder=builder,
+            )
+        except AuthError as e:
+            logger.warn("Failed to create join %r because %s", event, e)
+            raise e
 
         self.auth.check(event, auth_events=context.current_state)
 
@@ -915,7 +919,11 @@ class FederationHandler(BaseHandler):
             builder=builder,
         )
 
-        self.auth.check(event, auth_events=context.current_state)
+        try:
+            self.auth.check(event, auth_events=context.current_state)
+        except AuthError as e:
+            logger.warn("Failed to create new leave %r because %s", event, e)
+            raise e
 
         defer.returnValue(event)
 
@@ -1512,8 +1520,9 @@ class FederationHandler(BaseHandler):
 
         try:
             self.auth.check(event, auth_events=auth_events)
-        except AuthError:
-            raise
+        except AuthError as e:
+            logger.warn("Failed auth resolution for %r because %s", event, e)
+            raise e
 
     @defer.inlineCallbacks
     def construct_auth_difference(self, local_auth, remote_auth):
@@ -1689,7 +1698,12 @@ class FederationHandler(BaseHandler):
                 event_dict, event, context
             )
 
-            self.auth.check(event, context.current_state)
+            try:
+                self.auth.check(event, context.current_state)
+            except AuthError as e:
+                logger.warn("Denying new third party invite %r because %s", event, e)
+                raise e
+
             yield self._check_signature(event, auth_events=context.current_state)
             member_handler = self.hs.get_handlers().room_member_handler
             yield member_handler.send_membership_event(None, event, context)
@@ -1714,7 +1728,11 @@ class FederationHandler(BaseHandler):
             event_dict, event, context
         )
 
-        self.auth.check(event, auth_events=context.current_state)
+        try:
+            self.auth.check(event, auth_events=context.current_state)
+        except AuthError as e:
+            logger.warn("Denying third party invite %r because %s", event, e)
+            raise e
         yield self._check_signature(event, auth_events=context.current_state)
 
         returned_invite = yield self.send_invite(origin, event)