Why was Pope John XXIII’s meeting with the archbishop of Canterbury significant?

The meeting between Pope John XXIII and the archbishop of Canterbury was highly significant because it marked the first such encounter between the two leaders since the 14th century.1

This meeting reflected the pope's broader commitment to ecumenism and his desire to move toward Christian unity by setting aside historical hostilities. John XXIII’s openness to receiving Anglican, Protestant, and Eastern Orthodox leaders with extreme cordiality was a departure from previous Vatican norms and underscored his efforts to "bring the church up to date" (aggiornamento) and foster a spirit of reconciliation.1