Professor Russell A S Thomas is a Principal Research Scientist at the National Physical Laboratory and in 2020 was made the Science Area Leader for the Medical Radiation Science Group. He joined NPL in 1994, originally working on calibration services for photon and electron beam therapy level radiation and being trained as an operator for the NPL Radiation Dynamics Research Linear Accelerator. Since 2000, amongst other areas of research and development associated with the primary standards ionizing radiation, Russell has been involved in the development work of the group in therapy level proton dosimetry. This project has led to the creation of a new primary standard calorimeter specifically for proton beam therapy that can be operated directly in the clinical beam used to treat patients. It is hoped that the introduction of this new primary standard, combined with a new dosimetry code of practice for protons from IPEM, will result in considerably reducing the uncertainty on dose delivered to patients treated with this form of radiotherapy.  Russell is also a registered Clinical Scientist, a Fellow of the Institute of Physics and Engineering in Medicine and a Visiting Professor at the University of Surrey.