["JCMS: Journal of Common Market Studies, EarlyView. ", "\nAbstract\nThis article examines the section on European integration in the Joint Declaration by British Prime Minister John Major and his Irish counterpart Taoiseach Albert Reynolds in 1993. The Joint Declaration, also known as the ‘Downing Street Declaration’, was a pivotal moment in the Northern Ireland peace process. Using archival material and witness interviews, this article tracks the development of the text on Europe over time, revealing a negotiation process between officials and politicians in Dublin and London over the terms in which the European project would be discussed in the declaration. The role envisaged for Europe in bringing peace to Northern Ireland was progressively whittled down during this process, with the final text using vague, functional language, rather than the detailed discussion of the European dimension that is evident in earlier drafts. Whilst Sinn Féin's sceptical attitude to European integration clearly shaped the drafting process, as did concerns about further aggravating unionist sentiment, it was the political potency of Westminster Euroscepticism, especially during debates over the Maastricht Treaty, that ultimately dictated the final form of the wording on Europe in the declaration. Given the well‐recognised role the Downing Street Declaration had on establishing the principles enshrined in the 1998 Belfast/Good Friday Agreement and the subsequent debates over the European Union (EU) dimension of the peace process, which became highly politicised after the 2016 Brexit referendum, this negotiation process in the early 1990s clearly had a profound, if delayed, impact on politics in Northern Ireland, British–Irish and UK–EU relations."]