For his daily expenses, he stretched out on the pavement outside Balliol or Blackfriars, and dozed or read while waiting for money to collect in his hat. On a good day, he funnelled £30 worth of coins into his trouser pocket, concealing any notes in his trainers. A lifetime on the road had taught him how to economise. At lunchtime, he bought a ‘meal deal’ at Tesco for £4.50; on alternate afternoons, a latte from the stall beneath the Saxon Tower for £2.60. If it was raining hard, he forked out £22.50 to spend the night in a shelter for the homeless. Generally, though, he shunned hostels; the inmates were drug addicts or alcoholics who perceived Rougetel in terms of what materially could be begged, borrowed or filched off him.

Most nights, he walked back along the canal to St Mary’s, Iffley, after eating a second egg bap before McDonald’s closed at 2 a.m.

He lay down beneath the dog-tooth arch, sometimes on the bench in the porch, sometimes on the stone step – ‘surprisingly comfortable’ – and always a little nervous in case the vicar should discover him. It calmed something in Rougetel to know that an anchoress had lived here in the thirteenth century, Annora of Iffley, a widow who had holed herself up for nine years beside the church, in a timbered cell with a curtained window, surrounded only by religious books and writing materials, never stepping out into the world. On cold nights, under his tattered Bolivian blanket, reclining against his rucksack, Rougetel recalled his experiences on the road, and felt unexpectedly close to her.

The sun had come out. They crossed Norham Gardens at the entrance to the Parks. Flat bandages of cloud stretched over the trees. Near here a week before, Updark’s car had stopped to pick up Dyer.

The sob of a siren sucked Dyer back into the present. He wanted to ask Rougetel his opinion of America and Iran, but then recalled the bafflement in his eyes when Dyer had mentioned the nuclear deal. Dyer predicted that Rougetel would perceive the latest stand-off as not all that important in the great scheme: merely part of a continuity that stretched back, before Annora of Iffley even, to a period when Iran was the Achaemenid Empire and ruled the world – in its way so much larger than now – as the American president strove to dominate today.

Dyer’s bewilderment had increased on discovering how Rougetel occupied his days in Oxford. His abnegation was something that Dyer didn’t pretend to understand. It was as if they stood facing each other on opposite banks, and there floated between them a dark canal that was unbridgeable.