Add 5.717m to data values 1957-1972 to refer to RLR<br>Add 6.195m to data values 1973-1978 to refer to RLR<br>Add 5.946m to data values 1980-1996 to refer to RLR<br>Add 5.843m to data values 2001-2002 to refer to RLR<br>Add 6.003m to data values 2003 onwards to refer to RLR<br>RLR is 9.600m below primary benchmark Z Z Z