The Vatican announced on Monday that Pope Jon XXIII and John Paul II will be declared saints on April 27. The announcement was made in Latin by Pope Francis.

This is going to be the first time that two popes will be canonised at the same time.

"To celebrate them together is a sign of appreciation of the holiness of two popes who paid witness to our time," Rev Federico Lombardi, Vatican spokesman, explained through a press conference on Monday.

The date, April 27, is also the celebration of the Divine Mercy Sunday which John Paul II had upheld himself.

According to Rev Lombardi, the canonisation is "in the context of the 50th anniversary of the Second Vatican Council, and the universally heartfelt fame that surrounds John XXIII."

Rev Lombardi also said that the controversial Pope Benedict will attend the canonisation ceremony.

"There is no reason - either doctrinal or institutional - that he couldn't participate in the public ceremony," he explained.

The petition to canonise John Paul II had started even before he was buried. During his funeral, there were already people holding banners calling for John Paul II to be declared as saint.

In an interview with CNN, Vatican analyst John Allen explained that becoming a saint involved a qualifying process.

"You put a holy life and two miracles together, according to the Catholic system, you've got a saint. Pope Francis has decided that there already was a decree of heroic virtue saying that the man had lived a holy life. There already was one miracle certified for his beatification in 2000, so Pope Francis has decided he doesn't have to pass go, doesn't have to collect $200, he can go directly to sainthood," Mr Allen explained.

Mr Allen pointed out that the canonisation on earth simply formalises what had already took place in heaven.

"It's not like Karol Wojtyla, John Paul II, will suddenly become a saint when the canonisation ceremony occurs. The belief would be he is already in heaven with God, living the life of a saint. All that's going to happen when the ceremony occurs is that the church will officially recognise that," he added.