diff --git a/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/Muon/MuonAnalysisFitDataPresenter.h b/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/Muon/MuonAnalysisFitDataPresenter.h
index 5741696dbe7afe69e8c9ae3953f56eb7aa4ef947..739e84e2630a400e2bf047cb930f2236cf31e48d 100644
--- a/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/Muon/MuonAnalysisFitDataPresenter.h
+++ b/MantidQt/CustomInterfaces/inc/MantidQtCustomInterfaces/Muon/MuonAnalysisFitDataPresenter.h
@@ -118,10 +118,10 @@ public slots:
   void handleDatasetIndexChanged(int index);
   /// Open sequential fit dialog
   void openSequentialFitDialog();
-  /// Updates label to avoid overwriting existing results
-  void checkAndUpdateFitLabel(bool sequentialFit);
   /// Handles "fit raw data" selection/deselection
   void handleFitRawData(bool enabled, bool updateWorkspaces = true);
+  /// Perform pre-fit checks
+  void doPreFitChecks(bool sequentialFit);
 
 private:
   /// Generate names of workspaces to be created
@@ -149,8 +149,12 @@ private:
   void setUpDataSelector(const QString &wsName);
   /// Check if multiple runs are selected
   bool isMultipleRuns() const;
+  /// Updates label to avoid overwriting existing results
+  void checkAndUpdateFitLabel(bool sequentialFit);
   /// Update fit label to match run number(s)
   void updateFitLabelFromRuns();
+  /// Checks that runs are valid before fit
+  bool isRunStringValid();
   /// Fit browser to update (non-owning pointer to FitPropertyBrowser interface)
   MantidQt::MantidWidgets::IWorkspaceFitControl *m_fitBrowser;
   /// Muon fit browser to update (non-owning pointer to MuonFitPropertyBrowser
diff --git a/MantidQt/CustomInterfaces/src/Muon/MuonAnalysisFitDataPresenter.cpp b/MantidQt/CustomInterfaces/src/Muon/MuonAnalysisFitDataPresenter.cpp
index 58d9b4018a836e97091b918516aefb7597ba4592..3e45a154f6e8dd4730699fdf24079bf704b07fbf 100644
--- a/MantidQt/CustomInterfaces/src/Muon/MuonAnalysisFitDataPresenter.cpp
+++ b/MantidQt/CustomInterfaces/src/Muon/MuonAnalysisFitDataPresenter.cpp
@@ -139,8 +139,8 @@ void MuonAnalysisFitDataPresenter::doConnect() {
             SLOT(handleXRangeChangedGraphically(double, double)));
     connect(fitBrowser, SIGNAL(sequentialFitRequested()), this,
             SLOT(openSequentialFitDialog()));
-    connect(fitBrowser, SIGNAL(functionUpdateAndFitRequested(bool)), this,
-            SLOT(checkAndUpdateFitLabel(bool)));
+    connect(fitBrowser, SIGNAL(preFitChecksRequested(bool)), this,
+            SLOT(doPreFitChecks(bool)));
     connect(fitBrowser, SIGNAL(fitRawDataClicked(bool)), this,
             SLOT(handleFitRawData(bool)));
   }
@@ -374,9 +374,9 @@ MuonAnalysisFitDataPresenter::createWorkspace(const std::string &name,
   // load original data - need to get filename(s) of individual run(s)
   QStringList filenames;
   for (const int run : params.runs) {
-    filenames.append(
-        QString::fromStdString(MuonAnalysisHelper::getRunLabel(
-                                   params.instrument, {run})).append(".nxs"));
+    filenames.append(QString::fromStdString(MuonAnalysisHelper::getRunLabel(
+                                                params.instrument, {run}))
+                         .append(".nxs"));
   }
   try {
     // This will sum multiple runs together
@@ -831,5 +831,32 @@ void MuonAnalysisFitDataPresenter::updateFitLabelFromRuns() {
   }
 }
 
+/**
+ * Perform pre-fit checks and, if OK, tell the model it can go ahead with the
+ * fit.
+ * Checks are:
+ * - Has the fit label already been used? If so, ask user whether to overwrite.
+ * - Is the input run string valid?
+ * @param sequential :: [input] Whether fit is sequential or not
+ */
+void MuonAnalysisFitDataPresenter::doPreFitChecks(bool sequential) {
+  checkAndUpdateFitLabel(sequential);
+  if (isRunStringValid()) {
+    m_fitModel->continueAfterChecks(sequential);
+  } else {
+    g_log.error("Pre-fit checks failed: run string is not valid.\nCheck that "
+                "the data files are in Mantid's data search path.");
+  }
+}
+
+/**
+ * Check if the user has input a valid range of runs, i.e. that the red star is
+ * not shown on the interface
+ * @returns :: whether the runs are valid or not
+ */
+bool MuonAnalysisFitDataPresenter::isRunStringValid() {
+  return !m_dataSelector->getRuns().isEmpty();
+}
+
 } // namespace CustomInterfaces
 } // namespace MantidQt
diff --git a/MantidQt/CustomInterfaces/test/MuonAnalysisFitDataPresenterTest.h b/MantidQt/CustomInterfaces/test/MuonAnalysisFitDataPresenterTest.h
index a27b3fbbdda2b0ed32b2175e0e0189e97e9d1e6e..93971af4d224cc2781aaedfc9f6e70b23c2ae50d 100644
--- a/MantidQt/CustomInterfaces/test/MuonAnalysisFitDataPresenterTest.h
+++ b/MantidQt/CustomInterfaces/test/MuonAnalysisFitDataPresenterTest.h
@@ -82,7 +82,7 @@ public:
   MOCK_METHOD1(setSimultaneousLabel, void(const std::string &));
   MOCK_METHOD1(userChangedDataset, void(int));
   MOCK_CONST_METHOD0(rawData, bool());
-  MOCK_METHOD0(continueAfterChecks, void());
+  MOCK_METHOD1(continueAfterChecks, void(bool));
   void preFitChecksRequested(bool sequential) override{};
   GCC_DIAG_ON_SUGGEST_OVERRIDE
 };
diff --git a/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/IMuonFitDataModel.h b/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/IMuonFitDataModel.h
index 5d2638cf26130cf9ee65656ab986438e637be2e2..d8fbb4ca5b1459c520c597f761bd6918f354abf4 100644
--- a/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/IMuonFitDataModel.h
+++ b/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/IMuonFitDataModel.h
@@ -40,7 +40,7 @@ public:
   virtual void workspacesToFitChanged(int n) = 0;
   virtual void setSimultaneousLabel(const std::string &label) = 0;
   virtual void userChangedDataset(int index) = 0;
-  virtual void continueAfterChecks() = 0;
+  virtual void continueAfterChecks(bool sequential) = 0;
 signals:
   virtual void preFitChecksRequested(bool sequential) = 0;
 };
diff --git a/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/MuonFitPropertyBrowser.h b/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/MuonFitPropertyBrowser.h
index 50ad0f3a66b03757bb9cb867be6ad2973d2a565b..4ba2f013460f4d01bd0b0f4d7c8f600722f5a196 100644
--- a/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/MuonFitPropertyBrowser.h
+++ b/MantidQt/MantidWidgets/inc/MantidQtMantidWidgets/MuonFitPropertyBrowser.h
@@ -79,7 +79,7 @@ public:
   /// Set multiple fitting mode on or off
   void setMultiFittingMode(bool enabled) override;
   /// After fit checks done, continue
-  void continueAfterChecks() override;
+  void continueAfterChecks(bool sequential) override;
 
 public slots:
   /// Perform the fit algorithm
diff --git a/MantidQt/MantidWidgets/src/MuonFitPropertyBrowser.cpp b/MantidQt/MantidWidgets/src/MuonFitPropertyBrowser.cpp
index ae4175746182c7499f50a0763d825454ad492c7a..aceb84e26e2bea5f961e2c7238ea1c054d540c78 100644
--- a/MantidQt/MantidWidgets/src/MuonFitPropertyBrowser.cpp
+++ b/MantidQt/MantidWidgets/src/MuonFitPropertyBrowser.cpp
@@ -282,11 +282,9 @@ void MuonFitPropertyBrowser::populateFunctionNames() {
 }
 
 /**
- * Updates function prior to running a fit
+ * Requests checks and updates prior to running a fit
  */
-void MuonFitPropertyBrowser::fit() {
-  emit functionUpdateAndFitRequested(false);
-}
+void MuonFitPropertyBrowser::fit() { emit preFitChecksRequested(false); }
 
 /**
  * Creates an instance of Fit algorithm, sets its properties and launches it.
@@ -376,10 +374,10 @@ void MuonFitPropertyBrowser::runSequentialFit() {
 }
 
 /**
- * Update function prior to running a sequential fit
+ * Requests checks and updates prior to running a sequential fit
  */
 void MuonFitPropertyBrowser::sequentialFit() {
-  emit functionUpdateAndFitRequested(true);
+  emit preFitChecksRequested(true);
 }
 
 /**
@@ -570,8 +568,13 @@ void MuonFitPropertyBrowser::setMultiFittingMode(bool enabled) {
   }
 }
 
-void MuonFitPropertyBrowser::continueAfterChecks() {
-  //TODO: implement
+/**
+ * The pre-fit checks have been successfully completed. Continue by emitting a
+ * signal to update the function and request the fit.
+ * @param sequential :: [input] Whether fit is sequential or not
+ */
+void MuonFitPropertyBrowser::continueAfterChecks(bool sequential) {
+  emit functionUpdateAndFitRequested(sequential);
 }
 
 } // MantidQt