Although a British mission to the Holy See was established in 1914, the diplomatic relationship was not on a basis of reciprocity. From 1938 the pope was represented in London not by a nuncio (the Vatican equivalent of an ambassador) but by an apostolic delegate whose mission was to the hierarchy alone and not the British government. The evolution of the nuncio question sheds light on the nature of Anglo-Vatican relations, the place of Catholicism in British public life, inter-church rapprochement and British foreign policy considerations. This article assesses the divergent positions of the Foreign and Home Offices. The former was sympathetic to a change of status, whereas the latter was cautious due to the opposition of the archbishop of Canterbury and concerns about anti-Catholicism. The nuncio question was also of great interest to the Irish government. It feared that a nuncio in London would exert jurisdiction over Northern Ireland and undermine the all-island unity of the Irish Catholic Church. The Northern Ireland Troubles and the support displayed by the apostolic delegate for British policy hastened the restoration of full ambassadorial relations between London and the Holy See in 1982, ending a diplomatic breach that had existed for more than four centuries. It paved the way for Pope John Paul II’s historic pastoral visit to Britain which helped to consolidate the position of Roman Catholicism in British national life.