diff --git a/form.php b/form.php
index 30c6c47..ba42700 100644
--- a/form.php
+++ b/form.php
@@ -56,6 +56,9 @@ public function definition() {
         $mform->addElement('hidden', 'activitytype', $activitytype);
         $mform->setType('activitytype', PARAM_PLUGIN);
 
+        // Add number activities warning
+	$mform->addElement('html', '<p>' . get_string('numactivitieswarning', 'report_editdates') . '</p>');
+
         // Invisible static element. Used as the holder for a validation message sometimes.
         $mform->addElement('static', 'topvalidationsite', '', '');
 
diff --git a/index.php b/index.php
index 87e8ef5..3ba4452 100644
--- a/index.php
+++ b/index.php
@@ -27,6 +27,8 @@
 require_once(dirname(__FILE__) . '/form.php');
 use core\report_helper;
 
+$enablefilterthreshold = get_config('report_editdates', 'enablefilterthreshold');
+
 $id = required_param('id', PARAM_INT);
 $activitytype = optional_param('activitytype', '', PARAM_PLUGIN);
 
@@ -76,6 +78,20 @@
 }
 core_collator::asort($activitytypes);
 
+// Append number of activities to the all activities option
+$activitytypes["all"] .= (' (' . $activitiesdisplayed . ')');
+
+// If activity count is above the threshold, activate the filter controls.
+if (!$activitytype && $activitiesdisplayed > $enablefilterthreshold) {
+    if (count($activitytypes) > 1) {
+        $activitytypekey = array_keys($activitytypes)[1];
+    } else {
+        $activitytypekey = array_keys($activitytypes)[0];
+    }
+    redirect(new moodle_url('/report/editdates/index.php',
+        array('id' => $id, 'activitytype' => $activitytypekey)));
+}
+
 // Creating the form.
 $baseurl = new moodle_url('/report/editdates/index.php', ['id' => $id]);
 $mform = new report_editdates_form(
diff --git a/lang/en/report_editdates.php b/lang/en/report_editdates.php
index 1b621c3..7c17a9c 100644
--- a/lang/en/report_editdates.php
+++ b/lang/en/report_editdates.php
@@ -41,6 +41,9 @@
 $string['editdates'] = 'Dates';
 $string['editdates:view'] = 'View edit dates course report';
 $string['editend'] = 'Prevent editing from cannot be less than Allow editing from';
+$string['enablefilterthreshold'] = 'Enable filter threshold';
+$string['enablefilterthresholddesc'] = 'Maximum number of activities before enabling filter.';
+$string['numactivitieswarning'] = 'With a large number of activites, this form may take a long time to display.';
 $string['editrestrictedaccess'] = 'Edit restricted access (opens a new window)';
 $string['event:reportviewed'] = 'Edit dates report viewed';
 $string['hasrestrictedaccess'] = '{$a} has restricted date access settings';
diff --git a/settings.php b/settings.php
index 2a1b517..f95063f 100644
--- a/settings.php
+++ b/settings.php
@@ -39,4 +39,9 @@
             get_string('timelinemaxdesc', 'report_editdates'),
             3,
             $options));
+    $settings->add(new admin_setting_configtext('report_editdates/enablefilterthreshold',
+            get_string('enablefilterthreshold', 'report_editdates'),
+            get_string('enablefilterthresholddesc', 'report_editdates'),
+            40,
+            PARAM_INT));
 }