Add 5.170m to data values 1901-1917 to refer to RLR<br>Add 3.260m to data values for 1918 to refer to RLR<br>Add 5.170m to data values 1918-1919 to refer to RLR<br>Add 3.260m to data values for 1919 to refer to RLR<br>Add 5.170m to data values 1920-1930 to refer to RLR<br>Add 3.260m to data values for 1930 to refer to RLR<br>Add 5.170m to data values for 1931 to refer to RLR<br>Add 3.260m to data values for 1931 to refer to RLR<br>Add 5.170m to data values 1932 onwards to refer to RLR<br>RLR is 9.600m below primary benchmark BM CROWSFOOT