diff --git a/wagtail/admin/compare.py b/wagtail/admin/compare.py
index 3c64f158f9..dc7a416e62 100644
--- a/wagtail/admin/compare.py
+++ b/wagtail/admin/compare.py
@@ -10,6 +10,11 @@ from django.utils.translation import gettext_lazy as _
 from wagtail.core import blocks
 
 
+def text_from_html(val):
+    # Return the unescaped text content of an HTML string
+    return BeautifulSoup(force_str(val), 'html5lib').getText()
+
+
 class FieldComparison:
     is_field = True
     is_child_relation = False
@@ -52,15 +57,18 @@ class TextFieldComparison(FieldComparison):
 class RichTextFieldComparison(TextFieldComparison):
     def htmldiff(self):
         return diff_text(
-            BeautifulSoup(force_str(self.val_a), 'html5lib').getText(),
-            BeautifulSoup(force_str(self.val_b), 'html5lib').getText()
+            text_from_html(self.val_a),
+            text_from_html(self.val_b)
         ).to_html()
 
 
 def get_comparison_class_for_block(block):
     if hasattr(block, 'get_comparison_class'):
         return block.get_comparison_class()
-    elif isinstance(block, blocks.CharBlock):
+    elif isinstance(block, (blocks.CharBlock, blocks.TextBlock)):
+        return CharBlockComparison
+    elif isinstance(block, blocks.RawHTMLBlock):
+        # Compare raw HTML blocks as if they were plain text, so that tags are shown explicitly
         return CharBlockComparison
     elif isinstance(block, blocks.RichTextBlock):
         return RichTextBlockComparison
@@ -89,7 +97,19 @@ class BlockComparison:
         return self.val_a != self.val_b
 
     def htmlvalue(self, val):
-        return self.block.render_basic(val)
+        """
+        Return an HTML representation of this block that is safe to be included
+        in comparison views
+        """
+        return escape(text_from_html(self.block.render_basic(val)))
+
+    def htmldiff(self):
+        html_val_a = self.block.render_basic(self.val_a)
+        html_val_b = self.block.render_basic(self.val_b)
+        return diff_text(
+            text_from_html(html_val_a),
+            text_from_html(html_val_b)
+        ).to_html()
 
 
 class CharBlockComparison(BlockComparison):
@@ -99,13 +119,12 @@ class CharBlockComparison(BlockComparison):
             force_str(self.val_b)
         ).to_html()
 
+    def htmlvalue(self, val):
+        return escape(val)
+
 
 class RichTextBlockComparison(BlockComparison):
-    def htmldiff(self):
-        return diff_text(
-            BeautifulSoup(force_str(self.val_a), 'html5lib').getText(),
-            BeautifulSoup(force_str(self.val_b), 'html5lib').getText()
-        ).to_html()
+    pass
 
 
 class StructBlockComparison(BlockComparison):
@@ -219,8 +238,8 @@ class StreamFieldComparison(FieldComparison):
         else:
             # Fall back to diffing the HTML representation
             return diff_text(
-                BeautifulSoup(force_str(self.val_a), 'html5lib').getText(),
-                BeautifulSoup(force_str(self.val_b), 'html5lib').getText()
+                text_from_html(self.val_a),
+                text_from_html(self.val_b)
             ).to_html()
 
 
diff --git a/wagtail/admin/tests/test_compare.py b/wagtail/admin/tests/test_compare.py
index 262f4ba91d..2348ba11f4 100644
--- a/wagtail/admin/tests/test_compare.py
+++ b/wagtail/admin/tests/test_compare.py
@@ -247,36 +247,151 @@ class TestStreamFieldComparison(TestCase):
         self.assertIsInstance(comparison.htmldiff(), SafeString)
         self.assertTrue(comparison.has_changed())
 
-    def test_htmldiff_escapes_value(self):
+    def test_htmldiff_escapes_value_on_change(self):
         field = StreamPage._meta.get_field('body')
 
         comparison = self.comparison_class(
             field,
             StreamPage(body=StreamValue(field.stream_block, [
-                ('text', "Original content", '1'),
+                ('text', "I <b>really</b> like original<i>ish</i> content", '1'),
             ])),
             StreamPage(body=StreamValue(field.stream_block, [
-                ('text', '<script type="text/javascript">doSomethingBad();</script>', '1'),
+                ('text', 'I <b>really</b> like evil code <script type="text/javascript">doSomethingBad();</script>', '1'),
             ])),
         )
 
-        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object"><span class="deletion">Original content</span><span class="addition">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</span></div>')
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">I &lt;b&gt;really&lt;/b&gt; like <span class="deletion">original&lt;i&gt;ish&lt;/i&gt; content</span><span class="addition">evil code &lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</span></div>')
         self.assertIsInstance(comparison.htmldiff(), SafeString)
 
-    def test_htmldiff_escapes_value_richtext(self):
+    def test_htmldiff_escapes_value_on_addition(self):
         field = StreamPage._meta.get_field('body')
 
         comparison = self.comparison_class(
             field,
             StreamPage(body=StreamValue(field.stream_block, [
-                ('rich_text', "Original content", '1'),
+                ('text', "Original <em>and unchanged</em> content", '1'),
             ])),
             StreamPage(body=StreamValue(field.stream_block, [
-                ('rich_text', '<script type="text/javascript">doSomethingBad();</script>', '1'),
+                ('text', "Original <em>and unchanged</em> content", '1'),
+                ('text', '<script type="text/javascript">doSomethingBad();</script>', '2'),
             ])),
         )
 
-        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object"><span class="deletion">Original content</span><span class="addition">doSomethingBad();</span></div>')
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original &lt;em&gt;and unchanged&lt;/em&gt; content</div>\n<div class="comparison__child-object addition">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_escapes_value_on_deletion(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('text', "Original <em>and unchanged</em> content", '1'),
+                ('text', '<script type="text/javascript">doSomethingBad();</script>', '2'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('text', "Original <em>and unchanged</em> content", '1'),
+            ])),
+        )
+
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original &lt;em&gt;and unchanged&lt;/em&gt; content</div>\n<div class="comparison__child-object deletion">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_richtext_strips_tags_on_change(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', "I <b>really</b> like Wagtail &lt;3", '1'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', 'I <b>really</b> like evil code &gt;_&lt; <script type="text/javascript">doSomethingBad();</script>', '1'),
+            ])),
+        )
+
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">I really like <span class="deletion">Wagtail &lt;3</span><span class="addition">evil code &gt;_&lt; doSomethingBad();</span></div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_richtext_strips_tags_on_addition(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', "Original <em>and unchanged</em> content", '1'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', "Original <em>and unchanged</em> content", '1'),
+                ('rich_text', 'I <b>really</b> like evil code &gt;_&lt; <script type="text/javascript">doSomethingBad();</script>', '2'),
+            ])),
+        )
+
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original and unchanged content</div>\n<div class="comparison__child-object addition">I really like evil code &gt;_&lt; doSomethingBad();</div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_richtext_strips_tags_on_deletion(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', "Original <em>and unchanged</em> content", '1'),
+                ('rich_text', 'I <b>really</b> like evil code &gt;_&lt; <script type="text/javascript">doSomethingBad();</script>', '2'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('rich_text', "Original <em>and unchanged</em> content", '1'),
+            ])),
+        )
+
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original and unchanged content</div>\n<div class="comparison__child-object deletion">I really like evil code &gt;_&lt; doSomethingBad();</div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_raw_html_escapes_value_on_change(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', "Original<i>ish</i> content", '1'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', '<script type="text/javascript">doSomethingBad();</script>', '1'),
+            ])),
+        )
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object"><span class="deletion">Original&lt;i&gt;ish&lt;/i&gt; content</span><span class="addition">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</span></div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_raw_html_escapes_value_on_addition(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', "Original <em>and unchanged</em> content", '1'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', "Original <em>and unchanged</em> content", '1'),
+                ('raw_html', '<script type="text/javascript">doSomethingBad();</script>', '2'),
+            ])),
+        )
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original &lt;em&gt;and unchanged&lt;/em&gt; content</div>\n<div class="comparison__child-object addition">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</div>')
+        self.assertIsInstance(comparison.htmldiff(), SafeString)
+
+    def test_htmldiff_raw_html_escapes_value_on_deletion(self):
+        field = StreamPage._meta.get_field('body')
+
+        comparison = self.comparison_class(
+            field,
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', "Original <em>and unchanged</em> content", '1'),
+                ('raw_html', '<script type="text/javascript">doSomethingBad();</script>', '2'),
+            ])),
+            StreamPage(body=StreamValue(field.stream_block, [
+                ('raw_html', "Original <em>and unchanged</em> content", '1'),
+            ])),
+        )
+        self.assertEqual(comparison.htmldiff(), '<div class="comparison__child-object">Original &lt;em&gt;and unchanged&lt;/em&gt; content</div>\n<div class="comparison__child-object deletion">&lt;script type=&quot;text/javascript&quot;&gt;doSomethingBad();&lt;/script&gt;</div>')
         self.assertIsInstance(comparison.htmldiff(), SafeString)
 
     def test_compare_structblock(self):
diff --git a/wagtail/tests/testapp/migrations/0048_rawhtmlblock.py b/wagtail/tests/testapp/migrations/0048_rawhtmlblock.py
new file mode 100644
index 0000000000..19c901dccf
--- /dev/null
+++ b/wagtail/tests/testapp/migrations/0048_rawhtmlblock.py
@@ -0,0 +1,21 @@
+# Generated by Django 3.0.4 on 2020-04-06 09:46
+
+from django.db import migrations
+import wagtail.core.blocks
+import wagtail.core.fields
+import wagtail.tests.testapp.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tests', '0047_restaurant_tags'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='streampage',
+            name='body',
+            field=wagtail.core.fields.StreamField([('text', wagtail.core.blocks.CharBlock()), ('rich_text', wagtail.core.blocks.RichTextBlock()), ('image', wagtail.tests.testapp.models.ExtendedImageChooserBlock()), ('product', wagtail.core.blocks.StructBlock([('name', wagtail.core.blocks.CharBlock()), ('price', wagtail.core.blocks.CharBlock())])), ('raw_html', wagtail.core.blocks.RawHTMLBlock())]),
+        ),
+    ]
diff --git a/wagtail/tests/testapp/models.py b/wagtail/tests/testapp/models.py
index 3938ed1627..586672d21b 100644
--- a/wagtail/tests/testapp/models.py
+++ b/wagtail/tests/testapp/models.py
@@ -29,7 +29,7 @@ from wagtail.contrib.forms.models import (
 from wagtail.contrib.settings.models import BaseSetting, register_setting
 from wagtail.contrib.sitemaps import Sitemap
 from wagtail.contrib.table_block.blocks import TableBlock
-from wagtail.core.blocks import CharBlock, RichTextBlock, StructBlock
+from wagtail.core.blocks import CharBlock, RawHTMLBlock, RichTextBlock, StructBlock
 from wagtail.core.fields import RichTextField, StreamField
 from wagtail.core.models import Orderable, Page, PageManager, PageQuerySet
 from wagtail.documents.edit_handlers import DocumentChooserPanel
@@ -972,6 +972,7 @@ class StreamPage(Page):
             ('name', CharBlock()),
             ('price', CharBlock()),
         ])),
+        ('raw_html', RawHTMLBlock()),
     ])
 
     api_fields = ('body',)