diff --git a/app/__init__.py b/app/__init__.py
index dcfcab6..f31ca4e 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -1,4 +1,4 @@
-from flask import Flask
+from flask import Flask, render_template, request
 from flask_assets import Environment
 from flask_talisman import Talisman
 from flask_wtf.csrf import CSRFProtect
@@ -47,6 +47,15 @@ def create_app(config_class=Config):
         ],
     }
 
+    @app.before_request
+    def maintenance_page() -> str | None:
+        if request.endpoint != "static" and app.config["MAINTENANCE_MODE"]:
+            return render_template(
+                "main/maintenance-mode.html", maintenance_ends_from=app.config["MAINTENANCE_ENDS_FROM"]
+            )
+
+        return None
+
     # Initialise app extensions
     app.static_folder = "static/dist/"
     assets.init_app(app)
diff --git a/app/templates/base.html b/app/templates/base.html
index 4971618..cacc191 100644
--- a/app/templates/base.html
+++ b/app/templates/base.html
@@ -37,6 +37,7 @@
   }) }}
   {% endblock phaseBanner %}
 
+  {% block backLinks %}
   <div class="global-actions">
     {% if request.path not in [url_for('main.download'), url_for('main.start_page')] %}
       {{ govukBackLink({
@@ -50,6 +51,7 @@
       <a href="{{ config['AUTHENTICATOR_HOST'] + '/sso/logout' }}" class="govuk-body govuk-link govuk-link--no-underline govuk-link--no-visited-state govuk-!-margin-left-4">Log out</a>
     </div>
   </div>
+  {% endblock backLinks %}
 {% endblock beforeContent %}
 
 {% block content %}
diff --git a/app/templates/main/maintenance-mode.html b/app/templates/main/maintenance-mode.html
new file mode 100644
index 0000000..605ed30
--- /dev/null
+++ b/app/templates/main/maintenance-mode.html
@@ -0,0 +1,26 @@
+{% extends "base.html" %}
+
+{% block pageTitle %}Sorry, the service is unavailable – {{ config['SERVICE_NAME'] }} – GOV.UK{% endblock pageTitle %}
+
+{% block backLinks %}{% endblock backLinks %}
+
+{# Override main width to two thirds #}
+{% set mainClasses = "govuk-main-wrapper-l govuk-!-width-two-thirds" %}
+
+{% block content %}
+  <div class="govuk-width-container">
+    <h1 class="govuk-heading-l">Sorry, the service is unavailable</h1>
+
+    {% if maintenance_ends_from %}
+    <p class="govuk-body">You will be able to use the service from {{ maintenance_ends_from }}</p>
+    {% else %}
+    <p class="govuk-body">You will be able to use the service later.</p>
+    {% endif %}
+
+    <p class="govuk-body">
+      If you need help, contact us at <a class="govuk-link" href="mailto:{{ config['CONTACT_EMAIL'] }}">{{ config['CONTACT_EMAIL'] }}</a>.
+      We aim to respond within 1 to 2 working days
+    </p>
+    <p class="govuk-body">Do not send your data return or any attachments to this email address.</p>
+  </div>
+{% endblock content %}
diff --git a/config/envs/default.py b/config/envs/default.py
index c3adce8..548fb1b 100644
--- a/config/envs/default.py
+++ b/config/envs/default.py
@@ -11,6 +11,10 @@ class DefaultConfig(object):
     FLASK_ROOT = str(Path(__file__).parent.parent.parent)
     FLASK_ENV = CommonConfig.FLASK_ENV
     FSD_LOG_LEVEL = logging.INFO
+
+    MAINTENANCE_MODE: bool = os.getenv("MAINTENANCE_MODE", "false").lower() in {"1", "true", "yes", "y", "on"}
+    MAINTENANCE_ENDS_FROM: str | None = os.getenv("MAINTENANCE_ENDS_FROM")
+
     CONTACT_EMAIL = os.environ.get("CONTACT_EMAIL", "fsd.support@levellingup.gov.uk").lower()
     CONTACT_PHONE = os.environ.get("CONTACT_PHONE", "12345678910")
     DEPARTMENT_NAME = os.environ.get("DEPARTMENT_NAME", "Department for Levelling Up, Housing and Communities")