However, post-Reformation, the practice — labelled a corrupt and ungodly trade by Luther and his Protestant followers — largely died out. Where relics are on show today, they tend to belong to an earlier generation of saints, dead for many centuries. The eyeball of Edward Oldcorne, a Catholic Recusant martyred under James I, was in an exhibition in Liverpool last year, but as a historical curiosity rather than an object of veneration. There are rare exceptions — one of them the perfectly preserved remains of the seer of Lourdes, Bernadette Soubirous, which lie in a glass coffin at Nevers in southern France. But they stay in one place. It is only Thérèse's relics that go on tour.

What makes the whole process even stranger is that she is such a recent saint — at least in the context of 2,000 years of handing out haloes by the Church. Canonised in 1925, Thérèse of the Child Jesus and of the Holy Face, to give her official title, belongs in fact and in spirit to the contemporary age. There are, for example, photographs of her, while her writings speak to an age of uncertainty, with their frank admission of prolonged dark nights of the soul and doubt that God even existed. 

Yet this modern saint is venerated in such a medieval way. And that peculiar combination of old and new that is at the heart of the cult of Thérèse finds eloquent expression in Lisieux in the Carmel chapel itself. Built in the early 19th century, when the convent was first established, its exterior is very much of its time-imposing, dignified, elaborate in its stained glass and swooping carved white stone angels. Yet the interior has been given a very up-to-the-minute facelift. An inner shell of honey-coloured wooden screens, all attached at irregular intervals to a bare metal shell, sits as a skin within a skin in the chapel. As a shrine it has one foot firmly planted in the present and the other unmistakably in the past.

Marie Françoise Thérèse Martin was born in Alençon, not far from Lisieux, in January 1873. Her father Louis was a watchmaker, but a dreamer who hankered after a hermit's life before eventually succumbing to a form of madness, while his more practical wife, Zélie, was a lacemaker. Devout Catholics both, they typically for their times produced nine children, of whom Thérèse was the youngest. Four — two boys and two girls — had already died when Thérèse came along. She was just four when her mother was killed by breast cancer. Her older sister, Pauline, initially took on mothering Thérèse before entering the Carmelite convent in Lisieux, where the family had moved after Zélie's death. The maternal void was then filled by another sister, Marie, until she too decided to follow Pauline into the enclosure. Thérèse, unsurprisingly, suffered an acute sense of abandonment as a youngster and was plagued by a series of what may have been psychosomatic illnesses, which included a violent trembling so severe that, at one stage, the doctors told her father to prepare for the death of another of his children.

"She certainly had a fairly troubled childhood," says Father Michael McGoldrick, the head of the Carmelites in Britain and one of the organisers of the forthcoming visit by her relics. "That is one of the aspects of Thérèse that people today can relate, especially those with difficult family backgrounds. She is like many of us. Until she was 13, I'd say she had a neurotic aspect to her personality. She found it hard to relate to other girls at school, where she was bullied."