diff --git a/app/__init__.py b/app/__init__.py
index 17b17c563..0fd40481c 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -127,10 +127,10 @@ def create_app():
     application.after_request(save_service_after_request)
     application.before_request(load_service_before_request)
 
+    @application.context_processor
     def _attach_current_service():
         return {'current_service': current_service}
 
-    application.context_processor(_attach_current_service)
     register_errorhandlers(application)
 
     setup_event_handlers()
@@ -338,10 +338,7 @@ def load_service_before_request():
         else session.get('service_id')
     from flask.globals import _request_ctx_stack
     if _request_ctx_stack.top is not None:
-        setattr(
-            _request_ctx_stack.top,
-            'service',
-            service_api_client.get_service(service_id)['data'] if service_id else None)
+        _request_ctx_stack.top.service = service_api_client.get_service(service_id)['data'] if service_id else None
 
 
 def save_service_after_request(response):
diff --git a/app/main/views/letters.py b/app/main/views/letters.py
index 27f0a4bf1..0458493ea 100644
--- a/app/main/views/letters.py
+++ b/app/main/views/letters.py
@@ -5,8 +5,11 @@ from app import current_service
 from app.main import main
 from app.utils import user_has_permissions
 
+
 @main.route("/services/<service_id>/letters")
 @login_required
 @user_has_permissions('manage_templates', admin_override=True)
 def letters(service_id):
+    if not current_service['can_send_letters']:
+        abort(403)
     return render_template('views/letters.html')
diff --git a/tests/__init__.py b/tests/__init__.py
index e23f597b5..c1ffb0d4f 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -40,9 +40,9 @@ def created_by_json(id_, name='', email_address=''):
 
 
 def service_json(
-    id_,
-    name,
-    users,
+    id_='1234',
+    name='Test Service',
+    users=None,
     message_limit=1000,
     active=False,
     restricted=True,
@@ -50,9 +50,12 @@ def service_json(
     reply_to_email_address=None,
     sms_sender=None,
     research_mode=False,
-    organisation='organisation-id',
+    can_send_letters=False,
+    organisation=None,
     branding='govuk'
 ):
+    if users is None:
+        users = []
     return {
         'id': id_,
         'name': name,
@@ -64,6 +67,7 @@ def service_json(
         'reply_to_email_address': reply_to_email_address,
         'sms_sender': sms_sender,
         'research_mode': research_mode,
+        'can_send_letters': can_send_letters,
         'organisation': organisation,
         'branding': branding,
         'created_at': str(datetime.utcnow())
diff --git a/tests/app/main/views/test_letters.py b/tests/app/main/views/test_letters.py
new file mode 100644
index 000000000..c2c6451a6
--- /dev/null
+++ b/tests/app/main/views/test_letters.py
@@ -0,0 +1,17 @@
+import pytest
+from flask import url_for
+
+from tests import service_json
+
+
+@pytest.mark.parametrize('can_send_letters, response_code', [
+    (True, 200),
+    (False, 403)
+])
+def test_letters_access_restricted(logged_in_client, mocker, can_send_letters, response_code):
+    service = service_json(can_send_letters=can_send_letters)
+    mocker.patch('app.service_api_client.get_service', return_value={"data": service})
+
+    response = logged_in_client.get(url_for('main.letters', service_id=service['id']))
+
+    assert response.status_code == response_code
diff --git a/tests/app/main/views/test_main_nav.py b/tests/app/main/views/test_main_nav.py
new file mode 100644
index 000000000..f0cf23870
--- /dev/null
+++ b/tests/app/main/views/test_main_nav.py
@@ -0,0 +1,26 @@
+from flask import url_for
+from bs4 import BeautifulSoup
+
+from tests import service_json
+
+
+def test_can_see_letters_if_allowed(logged_in_client, mocker):
+    service = service_json(can_send_letters=True)
+    mocker.patch('app.service_api_client.get_service', return_value={"data": service})
+
+    response = logged_in_client.get(url_for('main.service_settings', service_id=service['id']))
+
+    assert response.status_code == 200
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+    assert 'Letter templates' in page.find('nav', class_='navigation').text
+
+
+def test_cant_see_letters_if_not_allowed(logged_in_client, mocker):
+    service = service_json(can_send_letters=False)
+    mocker.patch('app.service_api_client.get_service', return_value={"data": service})
+
+    response = logged_in_client.get(url_for('main.service_settings', service_id=service['id']))
+
+    assert response.status_code == 200
+    page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+    assert 'Letter templates' not in page.find('nav', class_='navigation').text
diff --git a/tests/app/main/views/test_service_settings.py b/tests/app/main/views/test_service_settings.py
index cb26e0a9b..924cce7a2 100644
--- a/tests/app/main/views/test_service_settings.py
+++ b/tests/app/main/views/test_service_settings.py
@@ -1,12 +1,13 @@
+from unittest.mock import call, ANY, Mock
+
 import pytest
 from flask import url_for
+from bs4 import BeautifulSoup
+from werkzeug.exceptions import InternalServerError
 
 import app
 from app.utils import email_safe
 from tests import validate_route_permission, service_json
-from bs4 import BeautifulSoup
-from unittest.mock import ANY, Mock
-from werkzeug.exceptions import InternalServerError
 
 
 def test_should_show_overview(
@@ -814,3 +815,25 @@ def test_should_set_branding_and_organisations(
             branding='org',
             organisation='organisation-id'
         )
+
+
+def test_switch_service_enable_letters(logged_in_client, service_one, mocker):
+    mocked_fn = mocker.patch('app.service_api_client.update_service_with_properties', return_value=service_one)
+
+    response = logged_in_client.get(url_for('main.service_switch_can_send_letters', service_id=service_one['id']))
+
+    assert response.status_code == 302
+    assert response.location == url_for('main.service_settings', service_id=service_one['id'], _external=True)
+    assert mocked_fn.call_args == call(service_one['id'], {'can_send_letters': True})
+
+
+def test_switch_service_disable_letters(logged_in_client, mocker):
+    service = service_json("1234", "Test Service", [], can_send_letters=True)
+    mocker.patch('app.service_api_client.get_service', return_value={"data": service})
+    mocked_fn = mocker.patch('app.service_api_client.update_service_with_properties', return_value=service)
+
+    response = logged_in_client.get(url_for('main.service_switch_can_send_letters', service_id=service['id']))
+
+    assert response.status_code == 302
+    assert response.location == url_for('main.service_settings', service_id=service['id'], _external=True)
+    assert mocked_fn.call_args == call(service['id'], {"can_send_letters": False})
diff --git a/tests/conftest.py b/tests/conftest.py
index d257e5c14..0e01266e6 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1276,3 +1276,16 @@ def mock_update_whitelist(mocker):
 def client(app_):
     with app_.test_request_context(), app_.test_client() as client:
         yield client
+
+
+@pytest.fixture(scope='function')
+def logged_in_client(
+    client,
+    active_user_with_permissions,
+    mock_login,
+    mock_get_user,
+    mock_get_service,
+    mock_has_permissions
+):
+    client.login(active_user_with_permissions)
+    yield client