Religion may well be in decline among European youth but it is by no means dead. This weekend about 6,000 young Catholics will set off on a 75-mile walk from Paris to Chartres Cathedral — and as they walk they will all be praying and singing in Latin.

Pope Benedict XVI’s decision last year in his apostolic letter, Summorum pontificum, to revive the Tridentine Latin Mass, was seen as a turning back of the clock by some liberal Catholics but greeted with jubilation by some conservative Catholics.

Out of all of the reforms triggered by the Second Vatican Council, the introduction of a new Mass in 1969, replacing the Roman Missal of 1962, was the most controversial.

Instead of facing east with his back to the congregation, the priest now faced them and recited the words in the local language rather than Latin. While not technically banned, the Tridentine Mass soon fell out of use, but some groups of Catholics refused to give up their attachment to it.

This weekend’s annual three-day pilgrimage through northern France, which is in its 26th year, illustrates the appeal that the Tridentine Mass has for some young Catholics disenchanted with what they say is the lack of mystery, beauty and sacredness in the revised Mass.

Gregory Flash, 28, an investment banker from London, explains why he is taking part in the pilgrimage for the second year running: “The pilgrimage is a time of prayer, penance and fellowship. It’s great to be surrounded by thousands of Catholics around the same age who, despite their different nationalities, can sing and pray in the same language and in the same way.”

The pilgrims come from several countries, including Poland, Germany, Italy and the US, and include seminarians. Some bishops and even cardinals have joined them in previous years.

They begin their pilgrimage at 6am on Saturday at Notre Dame Cathedral in Paris, where a priest will bless them. Carrying banners and flags, they then snake their way through the south-western suburbs of the city and out into the countryside.

“At mid-morning we attend the first Mass of the pilgrimage. A priest sets up an altar in a forest and will celebrate a full sung Mass with a choir singing Gregorian chant,” Mr Flash says.

The pilgrims follow part of one of the ancient routes to the shrine of Santiago de Compostela in Spain. They walk in small groups. Some sing the rosary in Latin; others make their confession to one of the traditionalist priests who accompany them. On Saturday and Sunday nights they camp in fields.

“When we arrive at Chartres Cathedral, the local bishop usually greets us. We then have a solemn Mass. Those who can’t fit inside watch it on TV screens outside. Priests hear confessions in the side chapels or on plastic chairs in the cathedral square.”

Grace Readings, 23, who works as a PA to an MP, will be making her 13th pilgrimage. She first went as a pupil at St Michael’s School in Berkshire, which is run by the Society of St Pius X, a breakaway traditionalist group which the Pope is trying to lure back to Rome.