Diarmuid O’Brien is sitting by the floor-to-ceiling window in his office that overlooks the lush green Iveagh Gardens below. The Dubliner is relaxed and has settled back into life in Ireland after four years in Cambridge, where he led the famed university’s innovation output. Now, he is eight months into his new job at the helm of Research Ireland, the newly-established State agency tasked with the development of the country’s research and innovation capability. His appointment was widely viewed as something of a coup, given the scale of his former role in the UK. So, why has he returned? “I…