*Data 1944-April 1973 supplied already
corrected to TGZ (1944-89)*
Add 6.283m to data values up to April 1973 to refer to RLR (1983)
Add  5.978m to data values May 1973 onwards to refer to RLR (1983)
RLR (1983) is 10.2m below BM K 80/4
