Although Ireland had been subject to English rule since the 12th century, it was not until the Act of Union in 1800 that it formally became part of the UK. In 1922, twenty-six of Ireland's counties exited from the UK and formed the Irish Free State, however the six north-eastern counties (i.e. Northern Ireland) remained within the UK, and still do to this day. Up to this date, citizens of both jurisdictions could travel freely across the Irish Sea, which for a family historian is unfortunate as no passenger lists exist to track their movements. Notwithstanding this, we know that vast numbers of Irish immigrated to the UK, many to Liverpool, Glasgow, the industrial cities of the midlands and, of course, to London. Their numbers were so significant that their presence altered the cultural, social, ethnic and religious face of many towns. UK census records survive from as early as 1841 and many of our clients' ancestors have been located here, and in the vast array of other less well known sources that have survived from the 17th-20th centuries.