Lochlainn O'Raifeartaigh, who died on November 18, aged 67, was a distinguished physicist of international repute. He was one of the world-leaders in the theory of elementary particles. Like the institution he served, he was far better known outside Ireland than within. From 1960 to the time of his death, he was a Professor at the School of Theoretical Physics in the Dublin Institute for Advanced Studies (DIAS).