This article examines the evolution of the British Government’s position regarding the question of the sovereignty over Northern Ireland from the post-Partition era until the signing of the Good Friday Agreement, which celebrates its 20th anniversary this year, as well as the gradual adjustment of the strategy of the Irish republican movement on this question, which eventually led to the end of the IRA’s armed campaign. The analysis of the evolution of British legislation in relation to the status of Northern Ireland, the commitments that the British Government acquired through the Anglo-Irish Agreement, the Sunningdale Agreement, and the Downing Street Declaration and the evolution of the strategy of the Republican movement in each of these moments show that the issue of Irish sovereignty, which has returned to the forefront of the political debate within the framework of the Brexit negotiations and the UK-Irish border, played a key role in the political settlement reached twenty years ago.