On Tuesday the Irish President, Michael D. Higgins, begins a four-day state visit to the UK, the first since the founding of the Irish state 92 years ago. Here, a seasoned diplomatic observer reflects on how far both countries have come to reach this high point in their relations B ritain and Ireland’s complex relationship was well summed up by the late Seamus Heaney when he wrote about “differences between two islands linked and separated in various degrees by history and geography, language and culture”. These differences dominated the relationship from 1922 until the 1980s, when a process of reconciliation, inspired by the Northern Ireland politician John Hume (like Heaney, both a Nobel prizewinner and a product of St Columb’s Catholic secondary school in Derry