diff --git a/elcid/migrations/0069_auto_20230323_1653.py b/elcid/migrations/0069_auto_20230323_1653.py
new file mode 100644
index 000000000..8426a8fbd
--- /dev/null
+++ b/elcid/migrations/0069_auto_20230323_1653.py
@@ -0,0 +1,17 @@
+# Generated by Django 2.2.16 on 2023-03-23 16:53
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('elcid', '0068_remove_mergedmrn_upstream_merge_datetime'),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name='demographics',
+            constraint=models.CheckConstraint(check=models.Q(_negated=True, hospital_number__startswith=0), name='No initial zeros'),
+        ),
+    ]
diff --git a/elcid/models.py b/elcid/models.py
index 822a412df..e9e437138 100644
--- a/elcid/models.py
+++ b/elcid/models.py
@@ -42,11 +42,11 @@ class MergedMRN(models.Model):
 
 class PreviousMRN(models.Model):
     """
-    A mixin for subrecords to maintain an audit trail for occasions 
+    A mixin for subrecords to maintain an audit trail for occasions
     when an upstream MRN merge occurs and the merged MRN has elCID entries.
-    
+
     `previous_mrn` is the MRN in use at the time that this subrecord instance
-    was last created/edited with if that MRN is different from the current 
+    was last created/edited with if that MRN is different from the current
     value of `Demographics.hospital_number` attached to this instance.
     """
     previous_mrn = models.CharField(blank=True, null=True, max_length=256)
@@ -75,6 +75,14 @@ def age(self):
 
     class Meta:
         verbose_name_plural = "Demographics"
+        constraints = [
+            # The bitwise "not" here is actually how you do the negation of a Q expression
+            # https://docs.djangoproject.com/en/dev/topics/db/queries/#complex-lookups-with-q-objects
+            models.CheckConstraint(
+                check = ~models.Q(hospital_number__startswith=0),
+                name = 'No initial zeros',
+            ),
+        ]
 
 
 class ContactInformation(PatientSubrecord, ExternallySourcedModel):