diff --git a/localgov_core.module b/localgov_core.module
index 53d8ad2..ef43ee1 100644
--- a/localgov_core.module
+++ b/localgov_core.module
@@ -13,6 +13,7 @@ function localgov_core_theme($existing, $type, $theme, $path) {
     'localgov_page_header_block' => [
       'variables' => [
         'title' => '',
+        'subtitle' => NULL,
         'lede' => NULL,
       ],
       'render element' => 'block',
diff --git a/src/Event/PageHeaderDisplayEvent.php b/src/Event/PageHeaderDisplayEvent.php
index a0aae69..f5e77f6 100644
--- a/src/Event/PageHeaderDisplayEvent.php
+++ b/src/Event/PageHeaderDisplayEvent.php
@@ -32,6 +32,13 @@ class PageHeaderDisplayEvent extends Event {
    */
   protected $title = NULL;
 
+  /**
+   * The page sub title override.
+   *
+   * @var array|string|null
+   */
+  protected $subTitle = NULL;
+
   /**
    * Should the page header block be displayed?
    *
@@ -103,6 +110,26 @@ public function setTitle($title) {
     $this->title = $title;
   }
 
+  /**
+   * Sub title getter.
+   *
+   * @return array|string|null
+   *   The sub title.
+   */
+  public function getSubTitle() {
+    return $this->subTitle;
+  }
+
+  /**
+   * Sub title setter.
+   *
+   * @param array|string|null $sub_title
+   *   The sub title.
+   */
+  public function setSubTitle($sub_title) {
+    $this->subTitle = $sub_title;
+  }
+
   /**
    * Visibility getter.
    *
diff --git a/src/Plugin/Block/PageHeaderBlock.php b/src/Plugin/Block/PageHeaderBlock.php
index 74b02d1..ad7159a 100644
--- a/src/Plugin/Block/PageHeaderBlock.php
+++ b/src/Plugin/Block/PageHeaderBlock.php
@@ -69,6 +69,13 @@ class PageHeaderBlock extends BlockBase implements ContainerFactoryPluginInterfa
    */
   protected $title;
 
+  /**
+   * The page subtitle override.
+   *
+   * @var array|string|null
+   */
+  protected $subTitle;
+
   /**
    * The page lede override.
    *
@@ -149,6 +156,7 @@ public function __construct(array $configuration, $plugin_id, $plugin_definition
 
     // Set the title, lede, visibility and cache tags.
     $this->title = is_null($event->getTitle()) ? $this->getTitle() : $event->getTitle();
+    $this->subTitle = is_null($event->getSubTitle()) ? NULL : $event->getSubTitle();
     $this->lede = is_null($event->getLede()) ? $this->getLede() : $event->getLede();
     $this->visible = $event->getVisibility();
     $entityCacheTags = is_null($this->entity) ? [] : $this->entity->getCacheTags();
@@ -164,6 +172,7 @@ public function build() {
     $build[] = [
       '#theme' => 'localgov_page_header_block',
       '#title' => $this->title,
+      '#subtitle' => $this->subTitle,
       '#lede' => $this->lede,
     ];
 
diff --git a/templates/localgov-page-header-block.html.twig b/templates/localgov-page-header-block.html.twig
index c188800..95d1aef 100644
--- a/templates/localgov-page-header-block.html.twig
+++ b/templates/localgov-page-header-block.html.twig
@@ -15,7 +15,12 @@
 ] %}
 {% if title %}
 <div{{ attributes.addClass(classes) }}>
-  <h1 class="header">{{ title }}</h1>
+  <h1 class="header">
+    {{ title }}
+    {% if subtitle %}
+      <div class="header__subtitle">{{ subtitle }}</div>
+    {% endif %}
+  </h1>
   {% if lede %}
   <div class="subheader">{{ lede }}</div>
   {% endif %}
diff --git a/tests/localgov_core_page_header_event_test/src/EventSubscriber/PageHeaderSubscriber.php b/tests/localgov_core_page_header_event_test/src/EventSubscriber/PageHeaderSubscriber.php
index a9319ec..a21879b 100644
--- a/tests/localgov_core_page_header_event_test/src/EventSubscriber/PageHeaderSubscriber.php
+++ b/tests/localgov_core_page_header_event_test/src/EventSubscriber/PageHeaderSubscriber.php
@@ -51,6 +51,13 @@ public function setPageHeader(PageHeaderDisplayEvent $event) {
       $event->setLede($parent->body->summary);
       $event->setCacheTags(Cache::mergeTags($node->getCacheTags(), $parent->getCacheTags()));
     }
+
+    // Set subtitle from parent, and cache tags from the parent for page4 nodes.
+    if ($node->bundle() == 'page4') {
+      $parent = $node->parent->entity;
+      $event->setSubTitle($parent->title->value);
+      $event->setCacheTags(Cache::mergeTags($node->getCacheTags(), $parent->getCacheTags()));
+    }
   }
 
 }
diff --git a/tests/src/Functional/PageHeaderBlockTest.php b/tests/src/Functional/PageHeaderBlockTest.php
index 738b222..c3b516d 100644
--- a/tests/src/Functional/PageHeaderBlockTest.php
+++ b/tests/src/Functional/PageHeaderBlockTest.php
@@ -56,7 +56,9 @@ public function testPageHeaderBlockDisplay() {
       'status' => NodeInterface::PUBLISHED,
     ]);
     $this->drupalGet($page->toUrl()->toString());
-    $this->assertSession()->responseContains('<h1 class="header">' . $node_title . '</h1>');
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]');
+    $page_title = $query[0]->getText();
+    $this->assertEquals($page_title, $node_title);
     $this->assertSession()->pageTextNotContains($node_summary);
     $page->set('body', [
       'summary' => $node_summary,
@@ -64,7 +66,9 @@ public function testPageHeaderBlockDisplay() {
     ]);
     $page->save();
     $this->drupalGet($page->toUrl()->toString());
-    $this->assertSession()->responseContains('<h1 class="header">' . $node_title . '</h1>');
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]');
+    $page_title = $query[0]->getText();
+    $this->assertEquals($page_title, $node_title);
     $this->assertSession()->pageTextContains($node_summary);
 
     // Check title and lede display on a taxonomy term page.
@@ -77,7 +81,9 @@ public function testPageHeaderBlockDisplay() {
     ]);
     $term->save();
     $this->drupalGet($term->toUrl()->toString());
-    $this->assertSession()->responseContains('<h1 class="header">' . $term_name . '</h1>');
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]');
+    $page_title = $query[0]->getText();
+    $this->assertEquals($page_title, $term_name);
     $this->assertSession()->pageTextContains('All pages relating to ' . $term_name);
   }
 
@@ -100,9 +106,11 @@ public function testPageHeaderDisplayEvent() {
       'status' => NodeInterface::PUBLISHED,
     ]);
     $this->drupalGet($page1->toUrl()->toString());
-    $this->assertSession()->responseNotContains('<h1 class="header">' . $title . '</h1>');
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]');
+    $page_title = $query[0]->getText();
+    $this->assertNotEquals($page_title, $title);
     $this->assertSession()->pageTextNotContains($summary);
-    $this->assertSession()->responseContains('<h1 class="header">Overridden title</h1>');
+    $this->assertEquals($page_title, 'Overridden title');
     $this->assertSession()->pageTextContains('Overridden lede');
 
     // Check hidden page header block.
@@ -117,9 +125,20 @@ public function testPageHeaderDisplayEvent() {
       'status' => NodeInterface::PUBLISHED,
     ]);
     $this->drupalGet($page2->toUrl()->toString());
-    $this->assertSession()->responseNotContains('<h1 class="header">' . $title . '</h1>');
+
+    // There should be no h1 visible.
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]');
+    $this->assertEmpty($query);
+
+    // Using pageTextNotContains also fetches the title tag, so do an xpath on
+    // the body tag to check the title text is not present.
+    $body_query = $this->xpath('.//body');
+    $body_text = $body_query[0]->getText();
+    $this->assertStringNotContainsString($title, $body_text);
+
+    // Check summary and overridden title and summary not present in page.
     $this->assertSession()->pageTextNotContains($summary);
-    $this->assertSession()->responseNotContains('<h1 class="header">Overridden title</h1>');
+    $this->assertSession()->pageTextNotContains('Overridden title');
     $this->assertSession()->pageTextNotContains('Overridden lede');
 
     // Check cache tags override.
@@ -182,6 +201,48 @@ public function testPageHeaderDisplayEvent() {
 
     // Check the child page contains the updated parent summary.
     $this->assertSession()->pageTextContains('page 3 parent updated summary');
+
+    // Set up a page4 that can reference other page4 nodes with
+    // subtitle in header.
+    $this->createContentType(['type' => 'page4']);
+
+    FieldConfig::create([
+      'field_name' => 'parent',
+      'entity_type' => 'node',
+      'bundle' => 'page4',
+      'label' => 'Parent',
+      'cardinality' => -1,
+    ])->save();
+
+    $page4parent = $this->createNode([
+      'type' => 'page4',
+      'title' => 'page 4 parent title',
+      'body' => [
+        'summary' => 'page 4 parent summary',
+        'value' => '',
+      ],
+      'status' => NodeInterface::PUBLISHED,
+    ]);
+
+    $page4child = $this->createNode([
+      'type' => 'page4',
+      'title' => 'page 4 child title',
+      'body' => [
+        'summary' => 'page 4 child summary',
+        'value' => '',
+      ],
+      'parent' => [
+        'target_id' => $page4parent->id(),
+      ],
+      'status' => NodeInterface::PUBLISHED,
+    ]);
+
+    // Load the child page.
+    $this->drupalGet($page4child->toUrl()->toString());
+    $query = $this->xpath('.//h1[contains(concat(" ",normalize-space(@class)," ")," header ")]//div');
+    $page_subtitle = $query[0]->getText();
+    $this->assertEquals($page_subtitle, 'page 4 parent title');
+
   }
 
 }