Papal canonisations a lesson in subtle art of Catholic politics

Two nuns walk in St. Peter's square at the Vatican, April 25, 2014. Pope Francis will canonize on April 27 the late Pope John Paul II, who reigned from 1978 to 2005, and Pope John XXIII, who was pontiff from 1958 to 1963 and called the Second Vatican Council, a landmark meeting that modernised the Church. REUTERS/Stefano Rellandini

(Reuters) - When the late Popes John XXIII and John Paul II are declared saints on Sunday, the Vatican ceremony will be both a spiritual event for Roman Catholicism and a lesson in the subtle politics of the world's largest church.

Most of the world's 1.2 billion Catholics will generally agree that these two men, in their own ways, were holy and charismatic pastors who helped their 2,000-year-old Church to confront the challenges of the modern era.