diff --git a/app/notify_client/__init__.py b/app/notify_client/__init__.py
index 504af8c9f..768b5ceda 100644
--- a/app/notify_client/__init__.py
+++ b/app/notify_client/__init__.py
@@ -12,10 +12,17 @@ def _attach_current_user(data):
 
 
 class NotifyAdminAPIClient(BaseAPIClient):
+    def init_app(self, app):
+        self.base_url = app.config['API_HOST_NAME']
+        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
+        self.api_key = app.config['ADMIN_CLIENT_SECRET']
+        self.route_secret = app.config['ROUTE_SECRET_KEY_1']
+
     def generate_headers(self, api_token):
         headers = {
             "Content-type": "application/json",
             "Authorization": "Bearer {}".format(api_token),
+            "X-Custom-Forwarder": self.route_secret,
             "User-agent": "NOTIFY-API-PYTHON-CLIENT/{}".format(__version__)
         }
         return self._add_request_id_header(headers)
diff --git a/app/notify_client/api_key_api_client.py b/app/notify_client/api_key_api_client.py
index 3052ce838..404f7880d 100644
--- a/app/notify_client/api_key_api_client.py
+++ b/app/notify_client/api_key_api_client.py
@@ -10,11 +10,6 @@ class ApiKeyApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_api_keys(self, service_id, key_id=None):
         if key_id:
             return self.get(url='/service/{}/api-keys/{}'.format(service_id, key_id))
diff --git a/app/notify_client/billing_api_client.py b/app/notify_client/billing_api_client.py
index ab6e76e13..10e0ce948 100644
--- a/app/notify_client/billing_api_client.py
+++ b/app/notify_client/billing_api_client.py
@@ -7,11 +7,6 @@ class BillingAPIClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, application):
-        self.base_url = application.config['API_HOST_NAME']
-        self.service_id = application.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = application.config['ADMIN_CLIENT_SECRET']
-
     def get_billable_units(self, service_id, year):
         return self.get(
             '/service/{0}/billing/monthly-usage'.format(service_id),
diff --git a/app/notify_client/email_branding_client.py b/app/notify_client/email_branding_client.py
index b82981adc..cadafecc5 100644
--- a/app/notify_client/email_branding_client.py
+++ b/app/notify_client/email_branding_client.py
@@ -6,11 +6,6 @@ class EmailBrandingClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_email_branding(self, branding_id):
         return self.get(url='/email-branding/{}'.format(branding_id))
 
diff --git a/app/notify_client/events_api_client.py b/app/notify_client/events_api_client.py
index 859f22c85..c12b8b721 100644
--- a/app/notify_client/events_api_client.py
+++ b/app/notify_client/events_api_client.py
@@ -5,11 +5,6 @@ class EventsApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def create_event(self, event_type, event_data):
         data = {
             'event_type': event_type,
diff --git a/app/notify_client/inbound_number_client.py b/app/notify_client/inbound_number_client.py
index 9ece7e746..eeadc7aca 100644
--- a/app/notify_client/inbound_number_client.py
+++ b/app/notify_client/inbound_number_client.py
@@ -6,11 +6,6 @@ class InboundNumberClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_available_inbound_sms_numbers(self):
         return self.get(url='/inbound-number/available')
 
diff --git a/app/notify_client/invite_api_client.py b/app/notify_client/invite_api_client.py
index fab12a8f0..5c3a548ba 100644
--- a/app/notify_client/invite_api_client.py
+++ b/app/notify_client/invite_api_client.py
@@ -8,10 +8,9 @@ class InviteApiClient(NotifyAdminAPIClient):
         super().__init__("a" * 73, "b")
 
     def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
+        super().init_app(app)
+
         self.admin_url = app.config['ADMIN_BASE_URL']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
 
     def create_invite(self, invite_from_id, service_id, email_address, permissions, auth_type):
         data = {
diff --git a/app/notify_client/job_api_client.py b/app/notify_client/job_api_client.py
index 2766c53d8..8b4a85563 100644
--- a/app/notify_client/job_api_client.py
+++ b/app/notify_client/job_api_client.py
@@ -19,11 +19,6 @@ class JobApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     @staticmethod
     def __convert_statistics(job):
         results = defaultdict(int)
diff --git a/app/notify_client/letter_jobs_client.py b/app/notify_client/letter_jobs_client.py
index 62b2a7c93..efa35e696 100644
--- a/app/notify_client/letter_jobs_client.py
+++ b/app/notify_client/letter_jobs_client.py
@@ -6,11 +6,6 @@ class LetterJobsClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_letter_jobs(self):
         return self.get(url='/letter-jobs')['data']
 
diff --git a/app/notify_client/notification_api_client.py b/app/notify_client/notification_api_client.py
index bb4140066..9e80af511 100644
--- a/app/notify_client/notification_api_client.py
+++ b/app/notify_client/notification_api_client.py
@@ -5,11 +5,6 @@ class NotificationApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_notifications_for_service(
         self,
         service_id,
diff --git a/app/notify_client/organisations_api_client.py b/app/notify_client/organisations_api_client.py
index 4583abaf8..0c4b110fc 100644
--- a/app/notify_client/organisations_api_client.py
+++ b/app/notify_client/organisations_api_client.py
@@ -6,11 +6,6 @@ class OrganisationsClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_organisations(self):
         return self.get(url='/organisations')
 
diff --git a/app/notify_client/provider_client.py b/app/notify_client/provider_client.py
index c1c1cbf8e..8c9975b85 100644
--- a/app/notify_client/provider_client.py
+++ b/app/notify_client/provider_client.py
@@ -6,11 +6,6 @@ class ProviderClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_all_providers(self):
         return self.get(
             url='/provider-details'
diff --git a/app/notify_client/service_api_client.py b/app/notify_client/service_api_client.py
index 7a086c61e..d6119f409 100644
--- a/app/notify_client/service_api_client.py
+++ b/app/notify_client/service_api_client.py
@@ -12,11 +12,6 @@ class ServiceAPIClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, application):
-        self.base_url = application.config['API_HOST_NAME']
-        self.service_id = application.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = application.config['ADMIN_CLIENT_SECRET']
-
     def create_service(
         self,
         service_name,
diff --git a/app/notify_client/status_api_client.py b/app/notify_client/status_api_client.py
index 5f8a88bad..1a69e7281 100644
--- a/app/notify_client/status_api_client.py
+++ b/app/notify_client/status_api_client.py
@@ -6,10 +6,5 @@ class StatusApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_status(self, *params):
         return self.get(url='/_status', *params)
diff --git a/app/notify_client/template_statistics_api_client.py b/app/notify_client/template_statistics_api_client.py
index e6afb411a..749fdf0d4 100644
--- a/app/notify_client/template_statistics_api_client.py
+++ b/app/notify_client/template_statistics_api_client.py
@@ -5,11 +5,6 @@ class TemplateStatisticsApiClient(NotifyAdminAPIClient):
     def __init__(self):
         super().__init__("a" * 73, "b")
 
-    def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
-
     def get_template_statistics_for_service(self, service_id, limit_days=None):
         params = {}
         if limit_days is not None:
diff --git a/app/notify_client/user_api_client.py b/app/notify_client/user_api_client.py
index 42bb8268e..8b9e5643a 100644
--- a/app/notify_client/user_api_client.py
+++ b/app/notify_client/user_api_client.py
@@ -16,9 +16,8 @@ class UserApiClient(NotifyAdminAPIClient):
         super().__init__("a" * 73, "b")
 
     def init_app(self, app):
-        self.base_url = app.config['API_HOST_NAME']
-        self.service_id = app.config['ADMIN_CLIENT_USER_NAME']
-        self.api_key = app.config['ADMIN_CLIENT_SECRET']
+        super().init_app(app)
+
         self.max_failed_login_count = app.config["MAX_FAILED_LOGIN_COUNT"]
         self.admin_url = app.config['ADMIN_BASE_URL']
 
diff --git a/tests/app/notify_client/test_notify_admin_api_client.py b/tests/app/notify_client/test_notify_admin_api_client.py
index 398208b9c..112e43ced 100644
--- a/tests/app/notify_client/test_notify_admin_api_client.py
+++ b/tests/app/notify_client/test_notify_admin_api_client.py
@@ -4,7 +4,7 @@ from unittest.mock import patch
 import pytest
 import werkzeug
 from tests import service_json
-from tests.conftest import api_user_active, platform_admin_user
+from tests.conftest import api_user_active, platform_admin_user, set_config
 
 from app.notify_client import NotifyAdminAPIClient
 
@@ -76,23 +76,29 @@ def test_inactive_service_can_be_modified_by_platform_admin(app_, platform_admin
     assert ret == request.return_value
 
 
-def test_generate_headers_sets_standard_headers():
+def test_generate_headers_sets_standard_headers(app_):
     api_client = NotifyAdminAPIClient(SAMPLE_API_KEY, 'base_url')
+    with set_config(app_, 'ROUTE_SECRET_KEY_1', 'proxy-secret'):
+        api_client.init_app(app_)
 
     # with patch('app.notify_client.has_request_context', return_value=False):
     headers = api_client.generate_headers('api_token')
 
-    assert set(headers.keys()) == {'Authorization', 'Content-type', 'User-agent'}
+    assert set(headers.keys()) == {'Authorization', 'Content-type', 'User-agent', 'X-Custom-Forwarder'}
     assert headers['Authorization'] == 'Bearer api_token'
     assert headers['Content-type'] == 'application/json'
     assert headers['User-agent'].startswith('NOTIFY-API-PYTHON-CLIENT')
+    assert headers['X-Custom-Forwarder'] == 'proxy-secret'
 
 
 def test_generate_headers_sets_request_id_if_in_request_context(app_):
     api_client = NotifyAdminAPIClient(SAMPLE_API_KEY, 'base_url')
+    api_client.init_app(app_)
 
     with app_.test_request_context() as request_context:
         headers = api_client.generate_headers('api_token')
 
-    assert set(headers.keys()) == {'Authorization', 'Content-type', 'User-agent', 'NotifyRequestID'}
+    assert set(headers.keys()) == {
+        'Authorization', 'Content-type', 'User-agent', 'X-Custom-Forwarder', 'NotifyRequestID'
+    }
     assert headers['NotifyRequestID'] == request_context.request.request_id