IT MAY become known as the day of the four popes - an unprecedented event when two popes witnessed the canonisations of two others.

More than a million pilgrims converged on Rome on Sunday to see Pope Francis declare Pope John XXIII (1958-63) and Pope John Paul II (1978-2005) to be saints.

In a rare public appearance, Pope Emeritus Benedict XVI, who abdicated last year, attended the event and was seen embracing his successor.

In his homily, Pope Francis paid tribute to the faith that underpinned the greatness of the two saints. "They were priests, bishops, and popes of the 20th century," he said said in the presence of their relics - a phial of blood taken from St John Paul II, and a sliver of skin from St John XXIII.

"They lived through the tragic events of that century, but they were not overwhelmed by them. For them, God was more powerful; faith was more powerful - faith in Jesus Christ the Redeemer of man and the Lord of history."

Pope Francis described John Paul II as "the pope of the family", and John XXIII as a "servant-leader" and the "pope of openness to the Spirit".

Rather than present them as conflicting conservative and reforming figures of the Roman Catholic Church, as some commentators had suggested, Pope Francis said that they each shared the same modernising enterprise.

"John XXIII and John Paul II co-operated with the Holy Spirit in renewing and updating the Church in keeping with her pristine features, those features which the saints have given her throughout the centuries."

The canonisations were attended by nearly 100 foreign delegations. The Duke and Duchess of Gloucester represented the Queen, and the Most Revd Sir David Moxon, the Archbishop of Canterbury's representative to the Holy See, attended on behalf of Archbishop Welby. Also present were 150 cardinals and more than 700 bishops.

A double papal canonisation may not happen again for centuries. St Pius X, who died in 1914, is the only modern-day pope so far to have been made a saint - and no canonisation of a pope has ever been attended by two living popes.

Besides convening the Second Vatican Council, Pope John XXIII, an Italian, was known for his dedication to the cause of peace. He had witnessed the horrors of war when, as Fr Angelo Roncalli, he served as a field chaplain in the First World War. Later, as a Vatican diplomat, he helped Jews to flee Europe from the Nazis.

He was considered a "caretaker" by some when he was elected in 1958 at the age of 76, but his five years in office proved fruitful.

He is said to have played a part in helping to defuse the Cuban missile crisis, and his encyclical, Pacem in Terris (Peace on Earth), published eight weeks before his death in June 1963, was seminal, emphasising existing Roman Catholic social teaching by espousing the cause of democracy; the right to dissent; workers' rights; the dignity of women; justice between rich and poor nations; and disarmament.

John Paul II, the first non-Italian pope since the 16th century, had experienced both Nazi and Communist totalitarianism as Fr Karol Wojtyla. He was widely credited with helping to tear down the Iron Curtain in his native Poland.

He also made more than 100 foreign visits, wrote 14 encyclicals, and canonised more than 400 saints. No pope before had met so many people: 17.6 million pilgrims attended his general audiences during his 27 years in office, the second longest papacy in history.

John Paul II survived at least three assassination attempts, including the shooting by Mehmet Ali Agca in St Peter's Square in 1981.

Both he and John XXIII were enthusiastic about ecumenism and interfaith dialogue. They also sought to correct historical injustices towards Jewish people.

The project manager at the Council of Christians and Jews, the Revd Patrick Morrow, said that John XXIII paved the way for the declaration by the Second Vatican Council that the Jews were not responsible for the death of Jesus, and John Paul II led repentance for Christian anti-Semitism.

"In both cases, it is no exaggeration to speak of a 'revolution'," he said.

On Monday, the Archbishop of Canterbury's Representative to the Holy See, the Most Revd David Moxon, who attended the canonisation, said: "I was moved by the numbers and the commitment to honour their memory as a living example for the church universal. With John XXIII there is the reminder and the encouragement for us to trust the simple and humble ways of faith, hope, and love more than we might, as he did. With John Paul II there is the reminder and encouragement for us to be courageous and vigorous in our upholding of the ways of righteousness and justice, whatever the political circumstances, as he did.

"For Anglicans these two popes reached out to Archbishops of Canterbury in new ways; John XXIII to Archbishop Fisher privately, and John Paul II to Archbishops Runcie, Carey, and Williams publically. We value their ecumenical spirit and their genuine hopes for greater cooperation between our two communions"