If you have ever tried, innocently, to go somewhere you shouldn’t at the Vatican you are likely to be turned back by a poker-faced Swiss guard. The army he belongs to is both the smallest in the world and the oldest still serving -- it has protected the Pope for over 500 years and added colourful ceremonial to events at the headquarters of the worldwide Catholic Church.

A few days ago the Swiss Guard held its annual swearing-in ceremony (full works here) in a courtyard at the Vatican. This happens on May 6, the anniversary of the Stand of the Swiss Guards which took place during the sacking of Rome in 1527, when the Pope's Swiss guards held off troops loyal to the Habsburgs long enough for Pope Clement to escape. Many, if not all of them (147), died to save Clement.

Another group of Swiss Guards were slaughtered defending Marie Antoinette and Louis XVI during the French Revolution. Of the nine hundred Swiss Guards defending the Palace of the Tuileries on 10 August 1792, about six hundred were killed during the fighting or massacred after surrender. Foreign military service was outlawed by the revised Swiss Constitution of 1874, with the only exception being the Pontifical Swiss Guard.

The new recruits – 40 of them this year -- take the oath in their own language: French, German, Italian and ...Romansch, a Romance language spoken predominantly in the south-eastern Swiss canton of Grisons. They swear to defend the Pope with their own lives, unlikely as that necessity is today. They mostly monitor the rooms in which the Pope lives and works, and accompany him on trips abroad --- though not in their distinctive uniform, presumably.

Swiss are not normally thought of as a war-like people, but every man does military service, and has a gun at home. The spectacular uniform of the Swiss Guard (blue and yellow for Pope Julius II who founded them, red for the Medici family of Pope Clement) and armour must appeal to many boys, but to enter this army you must, in addition to having a Swiss passport, be a practising Catholic.

Candidates must also be of good reputation, unmarried and between 18 and 30 years of age. And, evidently, male. (No stories from the Vatican yet about “trans men” trying to get one of those stylish outfits, but watch this space…) Being a Swiss Guard is clearly a special sort of vocation.

Pope Francis told his new guards:

"Today you are not called to this heroic surrender of physical life, but to another sacrifice no less difficult: to serve the power of faith. Faith is a valid barrier to resisting the forces and powers of this earth, and above all to the 'prince of this world', who is the 'father of lies.'"