The pilgrims gave a roar of approval when the pontiff, speaking after his weekly blessing, said: “I encourage all of you, dear academics, to always be respectful of the opinions of others, and to seek the truth and the good with an open and responsible mind.”

The 80-year-old pontiff cancelled a planned speech at Rome’s La Sapienza university last Thursday after dozens of professors and students protested his presence at the secular school.

“I want especially to salute university youths, professors and all of you who have come today in such large numbers to St Peter’s Square to ... express your solidarity,” the pope said. In a rare unscripted exhortation at the end of the appearance from his apartment overlooking the iconic square, the  Pope said: “Let us go forward in this spirit of fraternity and love for freedom and truth, and common commitment for a brotherly and tolerant society.” The protest against the visit to La Sapienza, Italy’s largest and oldest university, was spearheaded by Marcello Cini, a professor emeritus of physics, who wrote to rector Renato Guarini complaining of an “incredible violation” of the school’s autonomy.

Sixty-seven professors and researchers of the university’s physics department, as well as radical students, joined in the call for the pope to stay away. The incident “was a shock for most Italians, whatever their opinions on other subjects,” said Marco Politi, a Vatican expert at the Italian daily La Repubblica.