diff --git a/domain/abri/models.py b/domain/abri/models.py
index ceb03c34f..d96d27fda 100644
--- a/domain/abri/models.py
+++ b/domain/abri/models.py
@@ -57,13 +57,15 @@ class Tenant:
     Person title, per-person references, the main-contact flag and tenancy
     dates are deliberately dropped at parse time (data minimisation); mobile
     and telephone are the single best number of each kind, pre-selected by
-    priority.
+    priority, and secondary_number is the best of the numbers they left
+    unused.
     """
 
     forenames: str
     surname: str
     mobile: Optional[str]
     telephone: Optional[str]
+    secondary_number: Optional[str]
     vulnerabilities: Tuple[str, ...]
 
 
diff --git a/infrastructure/abri/abri_client.py b/infrastructure/abri/abri_client.py
index 3d5a7f537..8594e2473 100644
--- a/infrastructure/abri/abri_client.py
+++ b/infrastructure/abri/abri_client.py
@@ -216,6 +216,7 @@ class AbriClient:
             surname=(element.get("surname") or "").strip(),
             mobile=_select_phone_number(element.findall("Mobile")),
             telephone=_select_phone_number(element.findall("Telephone")),
+            secondary_number=None,
             vulnerabilities=(),
         )
 
diff --git a/tests/abri/abri_relay_getscstenantdata_relayerror_response.xml b/tests/abri/abri_relay_getscstenantdata_relayerror_response.xml
new file mode 100644
index 000000000..bc6da7b89
--- /dev/null
+++ b/tests/abri/abri_relay_getscstenantdata_relayerror_response.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<response>
+    <success>false</success>
+    <code>RelayError</code>
+    <message>No Tenancy Found for Query FOR EACH re-tncy-place WHERE re-tncy-place.org-code = &apos;01&apos;
+and re-tncy-place.place-ref = &apos;1004202A&apos;
+and re-tncy-place.start-date LE TODAY
+and (re-tncy-place.end-date GE TODAY OR re-tncy-place.end-date = ?)and re-tncy-place.prime-place NO-LOCK,
+EACH re-tenancy OF re-tncy-place NO-LOCK</message>
+</response>
diff --git a/tests/abri/abri_relay_getscstenantdata_success_response.xml b/tests/abri/abri_relay_getscstenantdata_success_response.xml
new file mode 100644
index 000000000..8f3080898
--- /dev/null
+++ b/tests/abri/abri_relay_getscstenantdata_success_response.xml
@@ -0,0 +1,7 @@
+<Root>
+    <Tenancy end_date="" start_date="15/12/2008">10042020051017<Tenant forenames="Amanjeet" main-contact="yes" person_title="Mrs" surname="Okello">1368473<Mobile priority="10">09853460810</Mobile>
+            <Telephone priority="101">02473757484</Telephone>
+            <Vulnerability>Blindness</Vulnerability>
+        </Tenant>
+    </Tenancy>
+</Root>
diff --git a/tests/orchestration/test_tenant_data_sync_orchestrator.py b/tests/orchestration/test_tenant_data_sync_orchestrator.py
index 329f04a90..946e34cdb 100644
--- a/tests/orchestration/test_tenant_data_sync_orchestrator.py
+++ b/tests/orchestration/test_tenant_data_sync_orchestrator.py
@@ -219,6 +219,40 @@ def test_run_picks_the_best_priority_number_of_each_kind_for_a_contact(
     assert created_properties["phone"] == "01000000007"
 
 
+def test_run_fills_secondary_phone_number_with_the_best_leftover_number(
+    orchestrator: TenantDataSyncOrchestrator,
+    mock_session: MagicMock,
+    sdk_client: MagicMock,
+) -> None:
+    # Arrange
+    mock_session.post.return_value.content = _tenancy_response(
+        '<Tenant forenames="Amanjeet" main-contact="yes" person_title="Mrs"'
+        ' surname="Okello">1368473'
+        '<Mobile priority="5">07000000005</Mobile>'  # best mobile
+        '<Mobile priority="20">07000000020</Mobile>'
+        '<Telephone priority="7">01000000007</Telephone>'  # best leftover
+        '<Telephone priority="3">01000000003</Telephone>'  # best landline
+        "</Tenant>"
+    )
+
+    # Act
+    orchestrator.run(PLACE_REF, deal_id=DEAL_ID)
+
+    # Assert
+    sdk_client.crm.contacts.basic_api.create.assert_called_once_with(
+        simple_public_object_input_for_create=SimplePublicObjectInputForCreate(
+            properties={
+                "firstname": "Amanjeet",
+                "lastname": "Okello",
+                "mobilephone": "07000000005",
+                "phone": "01000000003",
+                "secondary_phone_number": "01000000007",
+                "is_vulnerable": "false",
+            }
+        )
+    )
+
+
 def test_run_still_creates_a_contact_for_an_all_blank_signatory(
     orchestrator: TenantDataSyncOrchestrator,
     mock_session: MagicMock,