diff --git a/handbook/troggle/datamodel.html b/handbook/troggle/datamodel.html
index ac0e5b93b..a84518bb6 100644
--- a/handbook/troggle/datamodel.html
+++ b/handbook/troggle/datamodel.html
@@ -5,7 +5,8 @@
 <title>Handbook Troggle Data Model</title>
 <link rel="stylesheet" type="text/css" href="/css/main2.css" />
 </head>
-<body><style>body { background: #fff url(/images/style/bg-system.png) repeat-x 0 0 }</style>
+<body>
+<style>body { background: #fff url(/images/style/bg-system.png) repeat-x 0 0 }</style>
 <h2 id="tophead">CUCC Expedition Handbook - troggle</h2>
 <h1>Troggle Data Model (python)</h1>
 
@@ -17,7 +18,55 @@
 Auto-generated on 3 April 2020 with <var>troggle$ python3 manage.py inspectdb</var>. (Omitting all the 'Meta' sub-classes. )<br>
 Several classes have been edited out of this file between then and 14 September 2023 as they have been deleted as troggle has been tidied up.
 <p>All the classes below inherit from the django class (models.Model) and are thereby made persistent in the database. All <a href="https://docs.djangoproject.com/en/1.11/ref/models/fields/">persistent instance variables</a> are defined with e.g. "models.BooleanField()" types which is why they look so strange to a normal python programmer.
-<p>See <a href="/admin/doc/models/">the online auto-documentation</a> for the current set of core objects and their instance variables and foreign keys (anything below with "models.ForeignKey" in the  type field is a foreign key. <br>
+<p>See <a href="/admin/doc/models/">the online auto-documentation</a> for the current set of core objects and their instance variables and foreign keys (anything below with "models.ForeignKey" in the  type field is a foreign key.
+  
+  <h4>Culling unused fields</h4>
+<p>[This section to be moved elsewhere?]
+<p>We have a "<a href="https://docs.djangoproject.com/en/5.2/howto/custom-management-commands/">Django management command</a>" to find any fields on the models which are unused fossils. Do a full database import locally on a development machine, then in the /troggle/ folder run:
+  <pre><code>uv run manage.py find_empty_fields</code></pre>
+This provides a report of which fields in the database are unused across all records. It was <em>entirely</em> written by Google Gemini AI in October 2025.
+<pre>
+
+🚀 Starting scan for empty or null fields across all models...
+
+
+🔍 Checking model: auth.Group
+  ✅ All fields contain data.
+
+🔍 Checking model: core.Expedition
+  ✅ All fields contain data.
+
+🔍 Checking model: core.Person
+  -> Field 'orderref' is completely empty or null.
+
+🔍 Checking model: core.PersonExpedition
+  -> Field 'slugfield' is completely empty or null.
+
+🔍 Checking model: core.QM
+  -> Field 'completion_date' is completely empty or null.
+
+🔍 Checking model: core.DrawingFile
+  -> Field 'dwgcontains' is completely empty or null.
+  -> Field 'survexfiles' is completely empty or null.
+
+🔍 Checking model: core.Cave
+  -> Field 'kataster_status' is completely empty or null.
+...
+</pre>
+The code for this is located in <var>find_empty_fields.py</var>:
+<pre>
+troggle/
+└── core/
+    ├── __init__.py
+    ├── models/
+    ├── management/
+    │   ├── __init__.py
+    │   └── commands/
+    │       ├── __init__.py
+    │       └── find_empty_fields.py   <-- this file
+    └── views/
+</pre>
+<h3>Troggle data architecture classes</h3>
 This webpage is manually maintained and may be out of date.<code><pre><span style="color: green"># This is an auto-generated Django model module.
 # You'll have to do the following manually to clean this up:
 #   * Rearrange models' order
@@ -372,6 +421,5 @@ Return to: <a href="trogintro.html">Troggle intro</a><br />
 Troggle index: 
 <a href="trogindex.html">Index of all troggle documents</a><br />
 
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+<hr /></body>
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