The Leper’s Companions appears to have been written in a state of heavenly innocence. But there is more to Julia Blackburn than that.

She is the daughter of the poet Thomas Blackburn, who, she has said, was ‘very wild and very, very violent’, but taught her that ‘words have the magical power to make sense of things’. This is the first of her books that can with certainty be called a novel – she has published three highly praised imaginative biographies – and is written as a series of visions, not unlike those of her fourteenth-century East Anglian predecessor, Julian of Norwich.

Not that there is any equivalent here to Dame Julian’s Revelations of Divine Love. Divine love was not an easy concept in the wretched, lice-ridden fishing village on the Suffolk coast in 1410 which has been consuming Blackburn for the past two years.

But this isn’t a historical novel mixed with a pastiche of medieval mysticism, it is a great story contemporarily treated. Fiction runs into autobiography and out again. The author/narrator who is often in the wings in Blackburn’s other books is here centre stage, commenting not on flamboyant international figures (one of the biographies is about Napoleon) but on people of no historical consequence at all. Hardly any of them even has a name.

She becomes part of these people, talks to them though they seldom answer, sleeps with them though they don ‘t seem to notice. On page one she tells us that she has lost someone she loved and must ‘shut the door on the present time’. She walks to the beach, sits facing the sea and lets the centuries vanish. The church behind her is new again, ‘of yellow stone’. Hovels with curious people around them are all along the shore. Something disgusting, maybe a mermaid, is lying in the sand. There is enough action following this quiet scene for a thousand-page novel, a novel as learned as Marguerite Youcenar’s, but in fact it is not a long book, and it gallops.

Four people are called to go on a pilgrimage to the Holy Land: a leper, a parish priest, a fisherman’s widow mourning her family lost at sea, and a shoemaker’s widow who once spent six days and nights shouting at God for allowing human suffering. They set off, the ghostly narrator flitting between them, with no jingling bridle or Chaucerian levity, but on foot in grey cloaks with red crosses, bewildered by what they are doing. The fisherman’s widow has never left her village before and walks ‘like a bullock going to slaughter’. From Great Yarmouth they cross to Holland and walk across Europe, over the Alps to Italy, to Venice, where they pause, light-headed. On by sea down the Adriatic –  plague in all the ports. A storm. A heavenly visitation. Horrific sickness and death at sea. At last the port of Jaffa and the Holy Sepulchre.

One of them is dead by now. The rest scatter. The enchanting widow finds love again. The priest nearly drowns in the River Jordan. Only the leper ploughs on, with his invisible twentieth-century companion, crossing deserts, sleeping in the caves of lions with the heads of men, being attacked by Bedouin. At last he vanishes, too.

The sole survivor to regain his bleak East Anglian shore places a flask of Jordan water in the church, where light from the Norfolk stained-glass angel can flow down on it, and it becomes most efficacious ‘against shipwreck and drowning’.

We end with the narrator on the beach again, gazing at the horizon. The village is gone. Not a hovel. Not a mermaid. The same yew tree stand in the churchyard but the church has faded. Only a scrap of feathered colour remains in the stained-glass window and there is no sign of the Jordan water. Villagers do not piss against the pillar in the nave but nor is there an unswerving priest copying the Book of Revelation all night long in his cell, in ink made from ‘oak apples from Aleppo and iron salts from Spain’.

‘The magical power of words’. It was all of two days after finishing this book before I realised another thing it is about. It is a novel about the writing of a novel. There is first the dreaming, then the shutting of the door against the present day, then the desert slog with the moments of bliss. Then the wonderful moment arrives when the desert begins to recede and we know that soon there will be antelopes and fruit trees and fair weather. When the narrator rides between two tall stones on the far side of the last wilderness and her final companion doesn’t follow, she knows that she is home again and in her right mind, the book finished. This novel can be read on many levels and each of them is an imaginative triumph.