diff -u b/src/DiffLayoutManager.php b/src/DiffLayoutManager.php
--- b/src/DiffLayoutManager.php
+++ b/src/DiffLayoutManager.php
@@ -94,5 +94,6 @@
   public function getDefaultLayout() {
     $plugins = $this->getPluginOptions();
-    return array_keys($plugins[0]);
+    list($plugin) = array_keys($plugins);
+    return $plugin;
   }
 }
diff -u b/src/Form/GeneralSettingsForm.php b/src/Form/GeneralSettingsForm.php
--- b/src/Form/GeneralSettingsForm.php
+++ b/src/Form/GeneralSettingsForm.php
@@ -4,10 +4,38 @@
 
 use Drupal\Core\Form\ConfigFormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\diff\DiffLayoutManager;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 class GeneralSettingsForm extends ConfigFormBase {
 
   /**
+   * The field diff layout plugin manager service.
+   *
+   * @var \Drupal\diff\DiffLayoutManager
+   */
+  protected $diffLayoutManager;
+
+  /**
+   * GeneralSettingsForm constructor.
+   *
+   * @param \Drupal\diff\DiffLayoutManager $diff_layout_manager
+   *   The diff layout manager service.
+   */
+  public function __construct(DiffLayoutManager $diff_layout_manager) {
+    $this->diffLayoutManager = $diff_layout_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('plugin.manager.diff.layout')
+    );
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function getFormId() {
@@ -58,7 +86,7 @@
       '#options' => $options,
     );
 
-    $layout_plugins = \Drupal::service('plugin.manager.diff.layout')->getDefinitions();
+    $layout_plugins = $this->diffLayoutManager->getDefinitions();
     $weight = count($layout_plugins) + 1;
     $layout_plugins_order = [];
     foreach ($layout_plugins as $id => $layout_plugin) {
diff -u b/src/Tests/AdminFormsTest.php b/src/Tests/AdminFormsTest.php
--- b/src/Tests/AdminFormsTest.php
+++ b/src/Tests/AdminFormsTest.php
@@ -91,33 +91,50 @@
     ];
     $this->drupalPostForm(NULL, $edit, t('Save and keep published'));
 
-    // Check all the links are displayed.
+    // Assert the diff display uses the classic layout.
     $node = $this->getNodeByTitle('greater_title');
     $this->drupalGet('node/' . $node->id() . '/revisions');
     $this->drupalPostForm(NULL, [], t('Compare'));
     $this->assertLink('Single Column');
     $this->assertLink('Markdown');
     $this->assertLink('Standard');
+    $text = $this->xpath('//tbody/tr[4]/td[2]');
+    $this->assertEqual(htmlspecialchars_decode(strip_tags($text[0]->asXML())), '<p>great_body</p>');
 
     // Change the settings of the layouts, disable the single column.
     $edit = [
       'layout_plugins[classic][weight]' => '11',
-      'layout_plugins[classic][enabled]' => TRUE,
-      'layout_plugins[markdown][enabled]' => TRUE,
+      'layout_plugins[single_column][enabled]' => FALSE,
     ];
     $this->drupalPostForm('admin/config/content/diff/general', $edit, t('Save configuration'));
 
-    // Check the revision display.
+    // Assert the diff display uses the markdown layout.
     $this->drupalGet('node/' . $node->id() . '/revisions');
     $this->drupalPostForm(NULL, [], t('Compare'));
     $this->assertResponse(200);
     $this->assertNoLink('Single Column');
     $this->assertLink('Markdown');
     $this->assertLink('Standard');
-    $this->assertText('great_title');
+    $text = $this->xpath('//tbody/tr[4]/td[2]');
+    $this->assertEqual(htmlspecialchars_decode(strip_tags($text[0]->asXML())), 'great_body');
 
-    // @todo verify order of the plugins and disable classic layout. Set the
-    // default layout during routing.
+    // Change the settings of the layouts, enable single column.
+    $edit = [
+      'layout_plugins[single_column][enabled]' => TRUE,
+      'layout_plugins[classic][enabled]' => FALSE,
+      'layout_plugins[markdown][enabled]' => FALSE,
+    ];
+    $this->drupalPostForm('admin/config/content/diff/general', $edit, t('Save configuration'));
+
+    // Assert the diff display uses the single column layout.
+    $this->drupalGet('node/' . $node->id() . '/revisions');
+    $this->drupalPostForm(NULL, [], t('Compare'));
+    $this->assertResponse(200);
+    $this->assertLink('Single Column');
+    $this->assertNoLink('Markdown');
+    $this->assertNoLink('Standard');
+    $text = $this->xpath('//tbody/tr[5]/td[2]');
+    $this->assertEqual(htmlspecialchars_decode(strip_tags($text[0]->asXML())), '<p>great_body</p>');
   }
 
 }
only in patch2:
unchanged:
--- a/config/install/diff.settings.yml
+++ b/config/install/diff.settings.yml
@@ -3,3 +3,13 @@ general_settings:
   context_lines_leading: 1
   context_lines_trailing: 1
   revision_pager_limit: 50
+  layout_plugins:
+    classic:
+      enabled: true
+      weight: -50
+    markdown:
+      enabled: true
+      weight: -49
+    single_column:
+      enabled: true
+      weight: -48
only in patch2:
unchanged:
--- a/diff.routing.yml
+++ b/diff.routing.yml
@@ -3,7 +3,6 @@ diff.revisions_diff:
   defaults:
     _controller: '\Drupal\diff\Controller\NodeRevisionController::compareNodeRevisions'
     _title: Diff General Settings
-    filter: 'classic'
   requirements:
     _access_node_revision: 'view'
   options:
only in patch2:
unchanged:
--- a/src/Form/RevisionOverviewForm.php
+++ b/src/Form/RevisionOverviewForm.php
@@ -3,6 +3,7 @@
 namespace Drupal\diff\Form;
 
 use Drupal\Core\Language\LanguageManagerInterface;
+use Drupal\diff\DiffLayoutManager;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\Core\Form\FormBase;
@@ -58,6 +59,12 @@ class RevisionOverviewForm extends FormBase {
    */
   protected $config;
 
+  /**
+   * The field diff layout plugin manager service.
+   *
+   * @var \Drupal\diff\DiffLayoutManager
+   */
+  protected $diffLayoutManager;
 
   /**
    * Constructs a RevisionOverviewForm object.
@@ -72,14 +79,17 @@ class RevisionOverviewForm extends FormBase {
    *   The renderer service.
    * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
    *   The language manager.
+   * @param DiffLayoutManager $diff_layout_manager
+   *   DiffLayoutManager service.
    */
-  public function __construct(EntityManagerInterface $entityManager, AccountInterface $currentUser, DateFormatter $date, RendererInterface $renderer, LanguageManagerInterface $language_manager) {
+  public function __construct(EntityManagerInterface $entityManager, AccountInterface $currentUser, DateFormatter $date, RendererInterface $renderer, LanguageManagerInterface $language_manager, DiffLayoutManager $diff_layout_manager) {
     $this->entityManager = $entityManager;
     $this->currentUser = $currentUser;
     $this->date = $date;
     $this->renderer = $renderer;
     $this->languageManager = $language_manager;
     $this->config = $this->config('diff.settings');
+    $this->diffLayoutManager = $diff_layout_manager;
   }
 
   /**
@@ -91,7 +101,8 @@ class RevisionOverviewForm extends FormBase {
       $container->get('current_user'),
       $container->get('date.formatter'),
       $container->get('renderer'),
-      $container->get('language_manager')
+      $container->get('language_manager'),
+      $container->get('plugin.manager.diff.layout')
     );
   }
 
@@ -348,6 +359,7 @@ class RevisionOverviewForm extends FormBase {
         'node' => $nid,
         'left_revision' => $vid_left,
         'right_revision' => $vid_right,
+        'filter' => $this->diffLayoutManager->getDefaultLayout(),
       )
     );
     $form_state->setRedirectUrl($redirect_url);