This introductory chapter provides a literature and historical review of the International System of Units putting the achievements of the candidate in context and demonstrating how the publications cited have made a sustained and distinguished contribution to the advancement of the field.

The chapter begins with a broad introduction to the importance of measurement and measurement units, before describing the development of measurement units and unit systems, leading up to the creation of the International System of Units (SI). The evolution of the SI is then briefly explained up until the last 15 years or so that relate to the candidate’s contributions. This most recent period is then explained in more detail with reference to how the candidates work has shaped the most recent development and advancement of the SI. In order to make clear the different contributions, these have been broken down into four themes: “The mole and amount of substance”, “Expansion to the range of SI prefixes”, “Angle and quantities with the unit one”, and “Explaining the benefits of the SI” with a detailed narrative provided for each section. Read together they provide a compelling demonstration of the candidate’s substantial and distinguished contribution to the development and advancement of the SI over the last 15 years.

Referencing in this document is used both to provide relevant background sources and to highlight the candidate’s published literature. To avoid confusion between these two sources of references the candidate’s published work appears as a numbered endnote list at the end of the document, referenced in the text in square brackets, whereas third party sources appear as footnotes to each page referenced by superscripted Roman numerals in the text (and where possible use open access publications or authoritative website references). The candidate’s reference list also clarifies the extent of the candidate’s role for any co-authored papers. This document is purposely discursive and accessible, aiming to explain the narrative arc and importance of the contributions, with the detailed technical explanations available in the literature cited.