Add 4.183m to data values 1962-1968 to refer to RLR<br>Add 6.718m to data values for 1968 to refer to RLR<br>Add 4.183m to data values 1968-1982 to refer to RLR<br>Add 6.718m to data values for 1983 to refer to RLR<br>Add 4.183m to data values 1983 onwards to refer to RLR<br>RLR is 16.000m below primary benchmark BM SFO-3-1974