They are known as the "Defenders of the Church" and this weekend the Vatican Swiss Guard celebrated 500 years of service.

In that time they have protected 42 successive popes, although more recently the Vatican has been guarded by Italian security forces and plainclothes police. But personal safety of the pope is still the guards' full responsibility.

The guards first arrived in Rome on 22 January 1506. At that time, Helvetian soldiers were employed as mercenaries, renowned for their courage and their loyalty.

There were many famous battles, but their most notable hour came in 1527, during the sack of Rome. Almost the entire guard was massacred by troops of the Holy Roman emperor Charles V on the steps of St Peter's Basilica.