No border checks are carried out within the Common Travel Area. All citizens in the region are free to go anywhere of the region to work, study, live, and have the same rights as the local people, including the right to study, to receive medical care, to vote, etc. For example, an UK high school graduate can study in a college in Ireland; An Irish old man can live his best life in retirement in UK; Any Briton can go to Ireland and get a job, etc.
For the UK government, Irish citizens are different from citizens of other EU countries. Irish citizens can naturally enjoy civil rights in the UK which are not subject to any immigration provision. A child born in the UK is automatically granted British citizenship if either parent is an Irish citizen. Residents of other EU countries reside in the UK may be affected after Brexit, but Irish residents will not be affected.
This is why there is a growing number of applicants looking to live in the UK through the Irish Immigrant Investor Program, which has been growing every year since the program began in 2012. In 2018, 422 applications were accepted, hit a record high for six consecutive years of growth. Meanwhile, as the time of the formal Brexit comes, some Britons who do not want to lose their EU citizenship hope to hold Irish passports in order to retain their EU citizenship, leading to an overall surge in applications. The chart below shows that from 2018 to May 2019, there are 452 applications related to Ireland Immigrant Investor Program.
(Data from IMI/ The Department of Justice and Equality)
（Left: Number of applications / Right: Number of approvals）