Cyril Dix obituary

My father, Cyril Dix, who has died aged 97, was a research physicist who led the team of scientists that, in the early 1980s, established the international definition of how long a metre actually is.

The metre had, since 1791, been defined only by the length of a brass rod kept in a cellar in Paris. But in 1983 Cyril led a team at the National Physical Laboratory (NPL) in Teddington, Middlesex, which came up with a new, more precise international measurement that is now independent of any physical artefact and so gives an absolutely standard definition of the length of a metre anywhere in the world.