During the First World War, many French soldiers in the trenches would carry with them a copy of Story of a Soul. Those who survived travelled to Lisieux to donate their medals, which sit in rows in a display case in the museum next to the Carmel. Miraculous cures thanks to Thérèse's intercession with God began to be reported. "I had been diagnosed with a tumour," reads one of the marble plaques, originally in the chapel, now on the wall of the museum, signed GR and dated 1921, "Sister Thérèse saved me."

There may well have been a political dimension to Thérèse's elevation to sainthood in the post-First World War years — a tonic for a nation exhausted by war, or even a poke in the eye from the Vatican for the dominant secularism and anti-clericalism of the French government. Yet Thérèse is not simply the product of church-state machinations. 

She became genuinely popular as soon as people read her book. By the time of her canonisation in 1925, 410,000 copies of Story of a Soul had been printed. Rome's endorsement merely served to unleash a second wave of interest around the world. By the early 1930s, more than two million copies of an abridged version of the autobiography had been sold. 

Pilgrim numbers peaked at two million in 1997, Thérèse's centenary, when she became only the third woman to be declared a Doctor of the Church. It was in preparation for this anniversary that the first overseas tour by her relics was agreed — a short hop to Belgium in 1996. Next up was Italy, a bit further but still over land. Brazil and then the US, though, moved the whole operation on to a different scale altogether.

Sister Monique Marie works with the rector of Lisieux Basilica to organise the tours and often accompanies the reliquary. Although she wears a brown and white habit like the Carmelites, she belongs to a small, recently founded French congregation of sisters whose mission is in the world rather than in the enclosure. "It is not bones that people meet when they come to see the reliquary," she explains in a formula of words that I hear repeated every time I broach with officials at Lisieux the ghoulish aspect of touring Thérèse's remains. "It is a reaction. They are meeting a friend. Sometimes there is something difficult in their lives and they can leave all these difficult things to Thérèse as a friend." 

The reliquary remains closed at all times and is displayed behind a glass screen. What precisely do people do when they approach it? "It depends on the culture," says Sister Monique Marie. "In South America, you can't see the reliquary because everybody is crowding round it, wanting to touch it. We had to call the policemen, but in China, they are all standing one metre away and no one touches. For me, we are not angels. It is important to touch, just as you touch the arm of a friend."

And that intimate experience of the reliquary has, Sister Monique Marie reports, caused many to return to the practice of their faith. "It is very beautiful. Afterwards, people go to confession having not done it for years. They rediscover the Eucharist, the word of God and even the Church."