At the National Oceanography Centre (NOC) John leads the development of the digital ocean portfolio and has recently joined The Alan Turing Institute to co-direct the new Turing Research and Innovation Cluster in Digital Twins. Prior to his time at NOC he was at the Met Office where he was Head of the Ocean Forecasting R&D Department (OFRD) group and co-chair of the National Partnership for Ocean Prediction (NPOP). As Head of OFRD he had responsibility for developing models and satellite analyses for short-range ocean monitoring and forecasting and producing reanalyses for monitoring marine environment.

Prior to his career at the Met Office John worked for the Natural Environmental Research Council at Plymouth Marine Laboratory as a mathematical modeller in a biogeochemistry modelling team with the primary responsibility for implementing marine dynamical models.