“Because thou art lukewarm, and neither hot nor cold, I will spue thee out of my mouth.” (Revelations 3:16.) Whatever problems God had with his servant John Donne, lukewarmth was not among them. Seldom has a man burned with such fervent intensity. In the company of English love poets, with their cool ironising, their prophylactic mockery, their continence and equivocation, Donne blazes out like a winged unicorn in a dressage stable.

He had no sense of enough: infinity was not enough, hence the title of this wonderful book. Even when writing about death and extinction, he piles absence on absence. “I am the quintessence of nothingness,” he insists, and insists again, until he achieves the very opposite of nothingness: a tomb, yes, but one heaped with dark treasure. As Katherine Rundell says, he arrived in the world “book-hungry” and so he remained: like the “hydroptique (ever-thirsty) earth” of that poem, (“A Nocturnal upon St Lucy’s Day”) he sucked in ideas, impressions, sensations, connections, science, and poured them back transformed into poetic forms, sermons, treatises. He never had to husband his talent: there was always more where it came from.

Donne himself went through multiple iterations. Lawyer, adventurer, secretary, MP, diplomat, priest. When we think of Donne, Dean of St Paul’s, we forget he was once an Elizabethan swaggerer with a beautiful red mouth, sailing under the command of the Queen’s doomed favourite, the Earl of Essex, against an expected resurgence of the Spanish Armada.

Famously, the Donne of the poems is a different man from the Donne of prose: it was said that you fall in love with the one, and can barely tolerate the other. Rundell’s purpose here is to show us where these personae elide and intermix, as part of the universe that was John Donne. And in this, her enterprise follows that of her subject, whose work was always to conjoin those things that are apparently remote, and make a whole: like his image of the world map which, when folded edge to edge, brings the furthest extremities together.

The mixture of abiding concern to him was the cohesion of the soul and the body. He’d been born a Catholic of martyr stock, obliquely descended from Sir Thomas More. When he converted to Protestantism, he retained the old church’s preoccupation with the physical flesh, and married it to his adopted religion of the mind, to forge his own language for faith and for love.