diff --git a/grails-app/assets/javascripts/forms-knockout-bindings.js b/grails-app/assets/javascripts/forms-knockout-bindings.js
index 4778bfb..951b11b 100644
--- a/grails-app/assets/javascripts/forms-knockout-bindings.js
+++ b/grails-app/assets/javascripts/forms-knockout-bindings.js
@@ -1165,14 +1165,13 @@
         var dataLoader = new ecodata.forms.dataLoader(target.context, target.config);
         var dataLoaderConfig = target.get('computed');
         if (!dataLoaderConfig) {
-            throw "This extender can only be used with the metadata extender";
+            throw "This extender can only be used with the metadata extender and expects a computed property to be defined";
         }
         var dependencyTracker = ko.computed(function () {
             return dataLoader.prepop(dataLoaderConfig).done( function(data) {
                 target(data);
             });
-        });
-        //dependencyTracker.subscribe(function() { console.log("bananas")})
+        }); // This is a computed rather than a pureComputed as it has a side effect.
         return target;
     }
 
diff --git a/grails-app/assets/javascripts/forms.js b/grails-app/assets/javascripts/forms.js
index 2e72ad0..ac15063 100644
--- a/grails-app/assets/javascripts/forms.js
+++ b/grails-app/assets/javascripts/forms.js
@@ -860,7 +860,6 @@ function orEmptyArray(v) {
                     }
                 }
                 else if (metadata.constraints.type == 'pre-populated') {
-                    console.log("******************** Encountered pre-pop constraints for "+self.getName()+"***************************************")
                     var defaultConstraints = metadata.constraints.defaults || [];
                     var constraintsObservable = ko.observableArray(defaultConstraints);
                     if (!includeExcludeDefined) {
@@ -915,14 +914,14 @@ function orEmptyArray(v) {
             self.displayOptions = metadata.displayOptions;
         }
         self.load = function(data) {
-            console.log("Loading data for "+self.getName()+" : "+data)
-            self(data);
             if (constraintsInititaliser) {
                 constraintsInititaliser.always(function() {
-                    console.log("Re-Loading data for "+self.getName()+" : "+data)
                     self(data);
                 })
             }
+            else {
+                    self(data);
+            }
 
         }
     };
diff --git a/grails-app/assets/javascripts/knockout-utils.js b/grails-app/assets/javascripts/knockout-utils.js
index d6fa13a..7e09a50 100644
--- a/grails-app/assets/javascripts/knockout-utils.js
+++ b/grails-app/assets/javascripts/knockout-utils.js
@@ -91,16 +91,10 @@
             return (typeof root.modelAsJSON === 'function') ? root.modelAsJSON() : ko.toJSON(root);
         };
         var _initialState = ko.observable(getRepresentation());
-        console.log("****************** Initial state ******************")
-        console.log( _initialState())
 
         result.isDirty = ko.pureComputed(function () {
 
             var dirty = _isInitiallyDirty() || _initialState() !== getRepresentation();
-            if (dirty) {
-                console.log("******************* new state *******************")
-                console.log(getRepresentation())
-            }
             return dirty;
         });
         if (rateLimit) {
@@ -109,8 +103,6 @@
 
         result.reset = function () {
             _initialState(getRepresentation());
-            console.log("****************** Reset initial state ******************")
-            console.log( _initialState())
             _isInitiallyDirty(false);
         };
 
@@ -146,16 +138,14 @@
 
                 //just for subscriptions
                 getRepresentation();
-                console.log("****************** Initial state ******************")
-                console.log(getRepresentation())
+
                 //next time return true and avoid ko.toJS
                 _initialized(true);
 
                 //on initialization this flag is not dirty
                 return false;
             }
-            console.log("****************** New state ******************")
-            console.log(getRepresentation())
+
             //on subsequent changes, flag is now dirty
             return true;
         });
diff --git a/src/test/js/spec/DataLoaderExtenderSpec.js b/src/test/js/spec/DataLoaderExtenderSpec.js
new file mode 100644
index 0000000..765f1f1
--- /dev/null
+++ b/src/test/js/spec/DataLoaderExtenderSpec.js
@@ -0,0 +1,35 @@
+describe("dataLoader extender spec", function () {
+    var turf ;
+    beforeEach(function() {
+        jasmine.clock().install();
+    });
+    afterEach(function() {
+        jasmine.clock().uninstall();
+    });
+
+
+    it("should augment an observable with geojson type methods", function() {
+        var metadata = {
+            name:'item',
+            dataType:'text',
+            computed: {
+                source: {
+                    "context-path": "test"
+                }
+            }
+        };
+
+        var context = {
+            test:"test-value"
+        };
+        var config = {};
+
+        var dataItem = ko.observable().extend({metadata:{metadata:metadata, context:context, config:config}});
+        var withDataLoader = dataItem.extend({dataLoader:true});
+        jasmine.clock().tick();
+        expect(withDataLoader()).toEqual("test-value");
+
+    });
+
+
+});
diff --git a/src/test/js/spec/PrepopulationSpec.js b/src/test/js/spec/PrepopulationSpec.js
index b57fa6c..2a8f80b 100644
--- a/src/test/js/spec/PrepopulationSpec.js
+++ b/src/test/js/spec/PrepopulationSpec.js
@@ -75,4 +75,85 @@ describe("Pre-population Spec", function () {
             expect(result).toEqual({item1:"test"});
         });
     });
+
+    it("Should should support computing the pre-pop params via an expression", function() {
+        var context = {
+            data: {
+                item1: '1',
+                item2: '2'
+            }
+        };
+
+        var prepopConfig = {
+            source: {
+                url:'test',
+                params: [{
+                    "type":"computed",
+                    "expression":"2+2",
+                    name:"p1",
+                }]
+            },
+            mapping: []
+        };
+
+        var config = {
+            prepopUrlPrefix:'/'
+        };
+
+        var url;
+        var params;
+        spyOn($, 'ajax').and.callFake(function(p1,p2) {
+            url = p1;
+            params = p2;
+            return $.Deferred().resolve(context).promise();
+        });
+
+        var dataLoader = ecodata.forms.dataLoader(context, config);
+        dataLoader.getPrepopData(prepopConfig).done(function(result) {
+            expect(url).toEqual(config.prepopUrlPrefix+prepopConfig.source.url);
+            expect(params.data[0]).toEqual({name:"p1", value:4});
+            expect(params.dataType).toEqual('json');
+
+            expect(result).toEqual(context);
+        });
+    });
+
+    // This prevents making calls that will return errors
+    it("Should not make a remote call if required params are undefined", function() {
+        var context = {
+            data: {
+                item1: '1',
+                item2: '2'
+            }
+        };
+
+        var prepopConfig = {
+            source: {
+                url:'test',
+                params: [{
+                    "type":"computed",
+                    "expression":"x",
+                    name:"p1",
+                    required:true
+                }]
+            },
+            mapping: []
+        };
+
+        var config = {
+            prepopUrlPrefix:'/'
+        };
+
+        var called = false;
+
+        spyOn($, 'ajax').and.callFake(function(p1,p2) {
+            called = true;
+        });
+
+        var dataLoader = ecodata.forms.dataLoader(context, config);
+        dataLoader.getPrepopData(prepopConfig).done(function(result) {
+        });
+
+        expect(called).toEqual(false);
+    });
 });
\ No newline at end of file