diff --git a/app/main/views/sign_in.py b/app/main/views/sign_in.py
index 1ad7a2521..6d4a53996 100644
--- a/app/main/views/sign_in.py
+++ b/app/main/views/sign_in.py
@@ -16,6 +16,7 @@ from flask_login import (
 )
 
 from app import (
+    login_manager,
     user_api_client,
     service_api_client,
     invite_api_client
@@ -75,7 +76,14 @@ def sign_in():
             ).format(password_reset=url_for('.forgot_password'))
         ))
 
-    return render_template('views/signin.html', form=form)
+    return render_template('views/signin.html', form=form, again=bool(request.args.get('next')))
+
+
+@login_manager.unauthorized_handler
+def sign_in_again():
+    return redirect(
+        url_for('main.sign_in', next=request.path)
+    )
 
 
 def _get_and_verify_user(user, password):
diff --git a/app/templates/views/signin.html b/app/templates/views/signin.html
index 5b2ab7168..5e7ab5c8f 100644
--- a/app/templates/views/signin.html
+++ b/app/templates/views/signin.html
@@ -10,9 +10,19 @@
 
 <div class="grid-row">
   <div class="column-two-thirds">
-    <h1 class="heading-large">Sign in</h1>
 
-    <p>If you do not have an account, you can <a href="register">create one now</a>.</p>
+    {% if again %}
+      <h1 class="heading-large">You need to sign in again</h1>
+      <p>
+        We sign you out if you haven’t used Notify for a while.
+      </p>
+    {% else %}
+      <h1 class="heading-large">Sign in</h1>
+      <p>
+        If you do not have an account, you can
+        <a href="{{ url_for('.register') }}">create one now</a>.
+      </p>
+    {% endif %}
 
     <form method="post" autocomplete="nope">
       {{ textbox(form.email_address) }}
diff --git a/tests/app/main/views/test_accept_invite.py b/tests/app/main/views/test_accept_invite.py
index 1e6e1d9be..1a0102384 100644
--- a/tests/app/main/views/test_accept_invite.py
+++ b/tests/app/main/views/test_accept_invite.py
@@ -75,10 +75,13 @@ def test_if_existing_user_accepts_twice_they_redirect_to_sign_in(
     response = client.get(url_for('main.accept_invite', token='thisisnotarealtoken'), follow_redirects=True)
     assert response.status_code == 200
     page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
-    assert page.h1.string.strip() == 'Sign in'
-    flash_banners = page.find_all('div', class_='banner-default')
-    assert len(flash_banners) == 1
-    assert flash_banners[0].text.strip() == 'Please log in to access this page.'
+    assert (
+        page.h1.string,
+        page.select('main p')[0].text.strip(),
+    ) == (
+        'You need to sign in again',
+        'We sign you out if you haven’t used Notify for a while.',
+    )
 
 
 def test_existing_user_of_service_get_redirected_to_signin(
@@ -98,10 +101,13 @@ def test_existing_user_of_service_get_redirected_to_signin(
     response = client.get(url_for('main.accept_invite', token='thisisnotarealtoken'), follow_redirects=True)
     assert response.status_code == 200
     page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
-    assert page.h1.string.strip() == 'Sign in'
-    flash_banners = page.find_all('div', class_='banner-default')
-    assert len(flash_banners) == 1
-    assert flash_banners[0].text.strip() == 'Please log in to access this page.'
+    assert (
+        page.h1.string,
+        page.select('main p')[0].text.strip(),
+    ) == (
+        'You need to sign in again',
+        'We sign you out if you haven’t used Notify for a while.',
+    )
     assert mock_accept_invite.call_count == 1
 
 
@@ -130,10 +136,13 @@ def test_existing_signed_out_user_accept_invite_redirects_to_sign_in(
 
     assert response.status_code == 200
     page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
-    assert page.h1.string.strip() == 'Sign in'
-    flash_banners = page.find_all('div', class_='banner-default')
-    assert len(flash_banners) == 1
-    assert flash_banners[0].text.strip() == 'Please log in to access this page.'
+    assert (
+        page.h1.string,
+        page.select('main p')[0].text.strip(),
+    ) == (
+        'You need to sign in again',
+        'We sign you out if you haven’t used Notify for a while.',
+    )
 
 
 def test_new_user_accept_invite_calls_api_and_redirects_to_registration(
diff --git a/tests/app/main/views/test_platform_admin.py b/tests/app/main/views/test_platform_admin.py
index 195a1ecab..a27baf0d5 100644
--- a/tests/app/main/views/test_platform_admin.py
+++ b/tests/app/main/views/test_platform_admin.py
@@ -15,7 +15,7 @@ def test_should_redirect_if_not_logged_in(
 ):
     response = client.get(url_for('main.platform_admin'))
     assert response.status_code == 302
-    assert url_for('main.index', _external=True) in response.location
+    assert response.location == url_for('main.sign_in', next=url_for('main.platform_admin'), _external=True)
 
 
 def test_should_403_if_not_platform_admin(