On January 14, 1965, a meeting between the Taoiseach of Ireland (Sean Lemass) and the Prime Minister of Northern Ireland (Terence O’Neill) occurred for the first time since the partition of Ireland in 1922. The historic meeting at Stormont Castle signaled a thaw in relations between the two states.

O’Neill extended an innovation to Lemass to visit Belfast in early January, The meeting was planned for the following week and Lemass traveled to Belfast in secrecy. Although the meeting would be viewed as mostly positive in the Republic, it received mixed reviews in the North and O’Neill, an Ulster Unionist, faced strong opposition from his own party for the visit.

Lemass told O'Neill that he had long wanted such a meeting to "explore the possibility of practical co-operation in the interests of the whole of Ireland.”

The two leaders discussed cooperation between the two states on issues such as tourism, road systems, agriculture, customs, health services, and nuclear power.

A few weeks later, in February, O’Neill paid a reciprocal visit to Dublin.

The meetings between the leaders heralded a new (albeit short-lived) era of optimism for the two states.