Add 6.090m to data values 1929-1936 to refer to RLR<br>Add 4.870m to data values 1937-1965 to refer to RLR<br>Add 4.850m to data values 1966-1999 to refer to RLR<br>Subtract 0.961m from data values 2000 onwards to refer to RLR<br>RLR is 10.500m below primary benchmark BM d