Index: src/sas/sascalc/dataloader/readers/sesans_reader.py
===================================================================
--- src/sas/sascalc/dataloader/readers/sesans_reader.py	(revision a81af927e6ddd3f39a60348369c52ddcc94d02cb)
+++ src/sas/sascalc/dataloader/readers/sesans_reader.py	(revision e801a4ed13f7e36c2e7edac670f981c682489669)
@@ -86,4 +86,9 @@
             headers = input_f.readline().split()
 
+            self._insist_header(headers, "SpinEchoLength")
+            self._insist_header(headers, "Depolarisation")
+            self._insist_header(headers, "Depolarisation_error")
+            self._insist_header(headers, "Wavelength")
+
             data = np.loadtxt(input_f)
             if data.size < 1:
@@ -141,4 +146,10 @@
 
     @staticmethod
+    def _insist_header(headers, name):
+        if name not in headers:
+            raise RuntimeError(
+                "Missing {} column in spin echo data".format(name))
+
+    @staticmethod
     def _unit_conversion(value, value_unit, default_unit):
         """
Index: test/sasdataloader/test/sesans_examples/no_wavelength.ses
===================================================================
--- test/sasdataloader/test/sesans_examples/no_wavelength.ses	(revision e801a4ed13f7e36c2e7edac670f981c682489669)
+++ test/sasdataloader/test/sesans_examples/no_wavelength.ses	(revision e801a4ed13f7e36c2e7edac670f981c682489669)
@@ -0,0 +1,73 @@
+FileFormatVersion       1.0
+DataFileTitle           PMMA in Mixed Deuterated decalin
+Sample                  Ostensibly 40$ 100nm radius PMMA hard spheres in mixed deuterarted decalin.
+Thickness               2
+Thickness_unit          mm
+Theta_zmax              0.09
+Theta_zmax_unit         radians
+Theta_ymax              0.09
+Theta_ymax_unit         radians
+Orientation             Z
+SpinEchoLength_unit     A
+Depolarisation_unit     A-2 cm-1
+Wavelength_unit         A
+
+BEGIN_DATA
+SpinEchoLength Depolarisation Depolarisation_error 
+260.0 -1.42E-3 2.04E-3 1.612452
+280.8 -1.45E-3 1.87E-3 1.675709
+303.264 -1.64E-3 1.23E-3 1.741448
+327.525 -1.69E-3 1.17E-3 1.809765
+353.727 -2.23E-3 9.09E-4 1.880763
+382.025 -2.26E-3 8.58E-4 1.954546
+412.587 -2.41E-3 7.29E-4 2.031224
+445.594 -2.58E-3 6.75E-4 2.11091
+481.242 -2.88E-3 6.04E-4 2.193723
+519.741 -3.35E-3 5.56E-4 2.279783
+561.32 -3.60E-3 5.22E-4 2.369219
+606.226 -3.92E-3 4.91E-4 2.462166
+654.724 -4.36E-3 4.73E-4 2.558758
+707.102 -4.67E-3 4.54E-4 2.659139
+763.67 -4.91E-3 4.22E-4 2.763458
+824.764 -5.32E-3 3.88E-4 2.87187
+890.745 -5.43E-3 3.53E-4 2.984535
+962.005 -5.61E-3 3.28E-4 3.101621
+1038.97 -5.83E-3 3.07E-4 3.223306
+1122.08 -5.88E-3 2.91E-4 3.349746
+1211.85 -5.91E-3 2.73E-4 3.481164
+1308.8 -5.71E-3 2.61E-4 3.617734
+1413.5 -5.40E-3 2.49E-4 3.759654
+1526.58 -5.10E-3 2.41E-4 3.907147
+1648.71 -4.77E-3 2.34E-4 4.060431
+1780.6 -4.34E-3 2.26E-4 4.219716
+1923.05 -4.18E-3 2.20E-4 4.385259
+2076.9 -4.08E-3 2.16E-4 4.557302
+2243.05 -4.37E-3 2.13E-4 4.736085
+2422.49 -4.66E-3 2.10E-4 4.92188
+2616.29 -4.96E-3 2.06E-4 5.114968
+2825.59 -5.04E-3 2.03E-4 5.315628
+3051.64 -4.96E-3 1.99E-4 5.524165
+3295.77 -4.72E-3 1.97E-4 5.74088
+3559.43 -4.52E-3 1.92E-4 5.966096
+3844.19 -4.65E-3 1.93E-4 6.200153
+4151.72 -4.74E-3 1.96E-4 6.443384
+4483.86 -4.87E-3 1.99E-4 6.696163
+4842.57 -4.81E-3 2.05E-4 6.958858
+5229.98 -4.57E-3 2.09E-4 7.23186
+5648.38 -4.72E-3 2.17E-4 7.515571
+6100.25 -4.79E-3 2.23E-4 7.81041
+6588.27 -4.68E-3 2.28E-4 8.116816
+7115.33 -4.61E-3 2.32E-4 8.435242
+7684.55 -4.78E-3 2.46E-4 8.766157
+8299.32 -4.74E-3 2.46E-4 9.11006
+8963.26 -4.56E-3 2.50E-4 9.467449
+9680.32 -4.70E-3 2.58E-4 9.838862
+10454.7 -4.81E-3 2.64E-4 10.224823
+11291.1 -4.65E-3 2.69E-4 10.625959
+12194.4 -4.43E-3 2.79E-4 11.042826
+13170.0 -4.55E-3 3.01E-4 11.476062
+14223.6 -4.35E-3 3.20E-4 11.926274
+15361.5 -4.24E-3 3.51E-4 12.394152
+16590.4 -4.68E-3 4.12E-4 12.880373
+17917.6 -4.96E-3 4.98E-4 13.385664
+19303.4 -4.56E-3 5.98E-4 13.893668
Index: test/sasdataloader/test/utest_sesans.py
===================================================================
--- test/sasdataloader/test/utest_sesans.py	(revision a81af927e6ddd3f39a60348369c52ddcc94d02cb)
+++ test/sasdataloader/test/utest_sesans.py	(revision e801a4ed13f7e36c2e7edac670f981c682489669)
@@ -78,4 +78,14 @@
             self.loader,
             "sesans_examples/next_gen.ses")
+
+    def test_sesans_mandatory_headers(self):
+        """
+            Confirm that sesans files throw an exception if one of the mandator headers is missing.
+        """
+        self.assertRaises(
+            RuntimeError,
+            self.loader,
+            "sesans_examples/no_wavelength.ses")
+
 if __name__ == "__main__":
     unittest.main()
