Pope Francis toured the square in an open-topped vehicle shortly after 8am London time where about a million people were preparing for his first mass.
The Argentine was voted to replace Pope Benedict XVI by the conclave of cardinals last week.
He becomes the first leader of the Roman Catholic Church from the Americas.
As Pope Francis waves to his followers this morning, they chanted: “Long live the Pope!”
Then came his first official duties, beginning with donning his vestiges and venerating the tomb of St Peter.
He was then give his papal pallium, which is made of lambs’ wool to represent his position as the shepherd of his religion’s his flock, and the “fisherman’s ring”, which feature an image of St Peter holding two keys.
At this point, Pope Francis’s papacy officially began.
The ring he was presented was not in solid gold like the one worn by his predecessor, but second hand silver-plated gold.
The Pope then received the cardinals’ obedience and began his first mass in the company of 180 clergymen, US Vice-President Joe Biden and the spiritual head of the Orthodox Church, Patriarch Bartholomew – he is the first Orthodox patriarch to attend the papal inauguration mass since the Christianity branches split more than 1000 years ago.
Adolfo Nicolas, the superior general of Pope Francis’ Jesuit order, was also in attendance.
Image via Getty