diff --git a/public/app/themes/clarity/agency-switcher.php b/public/app/themes/clarity/agency-switcher.php
index 2c6f946bd..a0c428d90 100644
--- a/public/app/themes/clarity/agency-switcher.php
+++ b/public/app/themes/clarity/agency-switcher.php
@@ -1,15 +1,33 @@
 <?php
+
+use MOJ\Intranet\Agency;
+
 /*
 *  Agency switcher
 */
 get_header();
-?>
 
-  <main id="maincontent" class="u-wrapper l-main t-agency-switcher" role="main">
-    <h1 class="o-title o-title--page">Choose your agency or body</h1>
-    <p>Other agencies and bodies have their own specific intranet content available to view by visiting the links below. HMPPS and YJB links are external intranet websites not managed by this central MoJ intranet.</p>
-    <?php get_template_part('src/components/c-intranet-switcher/view'); ?>
-  </main>
+$oAgency = new Agency();
+$simpleHeader = !$oAgency->hasAgencyCookie();
 
+$heading = 'Choose your agency or body';
+$body = 'Other agencies and bodies have their own specific intranet content available to view by visiting the links 
+below. HMPPS and YJB links are external intranet websites not managed by this central MoJ intranet.';
+
+// If we're using the simple header, assume a new user and change the intro text to reflect this
+if ($simpleHeader) {
+    $heading = 'Welcome to the Ministry of Justice intranet';
+    $body = 'Please choose your agency or body to access the intranet content specific to your organisation.';
+}
+?>
+    <main id="maincontent" class="u-wrapper l-main t-agency-switcher" role="main">
+        <h1 class="o-title o-title--page">
+            <?= $heading ?>
+        </h1>
+        <p>
+            <?= $body ?>
+        </p>
+        <?php get_template_part('src/components/c-intranet-switcher/view'); ?>
+    </main>
 <?php
 get_footer();
diff --git a/public/app/themes/clarity/inc/agency.php b/public/app/themes/clarity/inc/agency.php
index d988b923c..674366922 100644
--- a/public/app/themes/clarity/inc/agency.php
+++ b/public/app/themes/clarity/inc/agency.php
@@ -167,6 +167,15 @@ public function getList()
         return $agencies_array;
     }
 
+    /*
+     * Check if the agency cookie is set
+     */
+    public function hasAgencyCookie(): bool
+    {
+        $agencyCookie = $_COOKIE['dw_agency'] ?? '';
+        return (bool)$agencyCookie;
+    }
+
     /***
      * Get the agency from cookie, and make sure it's in
      * the list, otherwise default to HQ
diff --git a/public/app/themes/clarity/inc/cookies.php b/public/app/themes/clarity/inc/cookies.php
index 1f3aad901..4eb11c4e3 100644
--- a/public/app/themes/clarity/inc/cookies.php
+++ b/public/app/themes/clarity/inc/cookies.php
@@ -38,10 +38,22 @@
         // a dw_agency cookie does not exist
     } else {
         $agency = $_COOKIE['dw_agency'] ?? '';
-
-        if (!$agencies->agencyExists($agency)) {
-            setcookie('dw_agency', $agency_default, $options);
-            $_COOKIE['dw_agency'] = $agency_default;
+        $slug = get_post_field('post_name');
+
+        if (
+            // If the agency cookie isn't set or is set to an invalid agency
+            !$agencies->agencyExists($agency) &&
+            // And the current page isn't the agency switcher, privacy notice, or accessibility page
+            !in_array($slug, ['agency-switcher', 'privacy-notice', 'accessibility'], true) &&
+            // And the user isn't logged in
+            !is_user_logged_in() &&
+            // And we're not in the admin area
+            $_SERVER['PHP_SELF'] != '/wp-admin/admin-ajax.php'
+        )
+        {
+            // Redirect to the agency switcher page
+            wp_safe_redirect('/agency-switcher/');
+            exit;
         }
     }
 });
diff --git a/public/app/themes/clarity/src/components/c-header-container/style.styl b/public/app/themes/clarity/src/components/c-header-container/style.styl
index 7340b6578..d642b43ec 100644
--- a/public/app/themes/clarity/src/components/c-header-container/style.styl
+++ b/public/app/themes/clarity/src/components/c-header-container/style.styl
@@ -9,4 +9,8 @@
 
 .c-header-container {
   margin-bottom: $spacing;
+
+  &--underlined {
+    border-bottom: 10px solid $defaultAgencyColour;
+  }
 }
diff --git a/public/app/themes/clarity/src/components/c-header-container/view.php b/public/app/themes/clarity/src/components/c-header-container/view.php
index 64033d409..a4a8f6ad0 100644
--- a/public/app/themes/clarity/src/components/c-header-container/view.php
+++ b/public/app/themes/clarity/src/components/c-header-container/view.php
@@ -1,10 +1,24 @@
-<header class="c-header-container" role="banner">
+<?php
+
+use MOJ\Intranet\Agency;
+
+$oAgency = new Agency();
+
+// Show a simplified header if the user has not yet chosen an agency
+$simpleHeader = !$oAgency->hasAgencyCookie();
+
+?>
+<header class="c-header-container<?= $simpleHeader ? " c-header-container--underlined" : ""?>" role="banner">
 
   <?php
+    // Hide the search bar and main nav bar if hideHeader is set, e.g. on first login before the user has chosen an agency
     get_template_part('src/components/c-logo-bar/view');
-    get_template_part('src/components/c-search-bar/view');
-    get_template_part('src/components/c-main-nav-bar/view');
-    ?>
+
+    if (!$simpleHeader) {
+      get_template_part('src/components/c-search-bar/view');
+      get_template_part('src/components/c-main-nav-bar/view');
+    }
+  ?>
   <!--[if lte IE 9]>
   <div class="u-message u-message--warning">
     You are using an old browser that may impact your web browsing experience. It is recommended you switch to use Firefox or a modern version of Internet Explorer if possible.
diff --git a/public/app/themes/clarity/src/components/c-logo-bar/view.php b/public/app/themes/clarity/src/components/c-logo-bar/view.php
index fe393805d..93d61f3cf 100644
--- a/public/app/themes/clarity/src/components/c-logo-bar/view.php
+++ b/public/app/themes/clarity/src/components/c-logo-bar/view.php
@@ -4,6 +4,10 @@
 
 $oAgency = new Agency();
 $activeAgency = $oAgency->getCurrentAgency();
+
+// Show a simplified header if the user has not yet chosen an agency
+$simpleHeader = !$oAgency->hasAgencyCookie();
+
 $header_logo = get_field(get_intranet_code() .'_header_logo', 'option');
 $logo = get_stylesheet_directory_uri() . '/dist/images/moj_logo_header.png';
 
@@ -24,13 +28,15 @@
         <div class="u-wrapper__stack--left">
             <a href="/" rel="home">
             <img class="c-logo-bar__logo" aria-hidden="true" src="<?= $logo ?>" alt="" />
-            <span class="agency-title l-half-section"><?= $activeAgency['label'] ?></span>
+            <!--  We hide the full header if the user hasn't selected an agency  -->
+            <!--  Default to 'Ministry of Justice' in the logo bar in this case  -->
+            <span class="agency-title l-half-section"><?= $simpleHeader ? 'Ministry of Justice' : $activeAgency['label'] ?></span>
             </a>
         </div>
 
         <div class="u-wrapper__stack--right">
             <?php if (get_query_var('name') !== 'agency-switcher') : ?>
-            <a href="/agency-switcher" class="c-logo-bar__switch">Switch to other intranet</a>
+            <a href="/agency-switcher" class="c-logo-bar__switch"><?= $simpleHeader ? 'Choose an agency' : 'Switch to other intranet' ?></a>
             <?php endif; ?>
         </div>
     </div>