Especialista em História, Numismática e Epigrafia Helenística. Foi curador de Moedas Gregas no Museu Britânico e serviu como Gestor de Investigação do Museu. Em 2007 foi membro do Instituto de Estudos Avançados em Princeton, e no mesmo ano tornou-se Curador de Moedas Gregas de Margaret Thompson na Sociedade Numismática Americana (ANS), Nova Iorque. De 2008 a 2014 foi Diretor Adjunto da ANS. Em 2014 mudou-se para New College, Oxford, para assumir o Tutorial Fellowship in Ancient History e foi nomeado Professor de História Antiga na Faculdade de Clássicos da Universidade de Oxford. Em julho de 2015 foi nomeado para a Curadoria Honorária no Museu Ashmolean e em outubro de 2019 tornou-se Diretor da Faculdade do Centro de Estudos de Documentos Antigos. Serviu como Secretário Honorário da Royal Numismatic Society e foi Secretário do Comité Sylloge Nummorum Graecorum (SNG) da Academia Britânica. Desde 2013 tem sido Diretor do Projeto Internacional SNG. Em 2012 realizou o Kraay Visitorship em Wolfson College e obteve a bolsa de estudo Robinson Visiting Scholarship em Ashmolean Museum, Oxford. Em 2014/5 foi o Professor de Metcalf do Instituto Arqueológico da América. Em 2015 foi eleito para o Comité do Conselho Numismático Internacional. Editor da série ANS-CUP, Guias para a Coinage of the Ancient World e da OUP Oxford Studies in Ancient Documents.Specialist in the history, numismatics and epigraphy of the Hellenistic world. He was Curator of Greek Coins at the British Museum and Head of Research at the Museum. In 2007 he was a member of the Institute for Advanced Study in Princeton and in the same year became Margaret Thompson Curator of Greek Coins at the American Numismatic Society (ANS), New York. From 2008-2014 he was Deputy Director of the Society. In 2014 he moved to New College, Oxford, to take up the Tutorial Fellowship in Ancient History and was appointed Professor of Ancient History in the Department of Classics. In July 2015 he was appointed Honorary Curator at the Ashmolean Museum and in October 2019 he became Director of the Faculty’s Center for the Study of Ancient Documents and he served as Honorary Secretary of the Royal Numismatic Society. He was Secretary of the Sylloge Nummorum Graecorum (SNG) Committee of the British Academy. Since 2013 he has been Director of the International SNG Project. In 2012 he held the Kraay Visitorship at Wolfson College and a Robinson Visiting Scholarship at the Ashmolean Museum in Oxford. In 2014/5 he was Metcalf Lecturer at the Archeological Institute of America. In 2015 he was elected to the Committee of the International Numismatic Council. He is editor of the ANS-CUP series, Guides to the Coinage of the Ancient World and the OUP series Oxford Studies in Ancient Documents.