Add 5.980m to data values 1967-1978 to refer to RLR<br>Add 5.909m to data values 1979-1997 to refer to RLR<br>Add 5.834m to data values 2001-2002 to refer to RLR<br>Add 5.984m to data values 2003 onwards to refer to RLR<br>RLR is 10.400m below primary benchmark BM 1