The trick, when rifling through the library of a practitioner, is to find the books with the notes written in the margins. I don’t know why – perhaps it was something they encouraged at Casterbrook – but I’ve never met a wizard yet who could resist jotting his thoughts down on somebody else’s work. The History of Ludlow by Thomas Wright Esq., MA, FRS, Hon. MRSL, 1850 had been extensively scribbled on as well as having obviously, judging by the stamp, been lifted from the Bodleian Library. There was quite a lot about wolves and their rampages in the tenth century alongside which Hugh, I recognised his handwriting, had written alas no more. One book caught my eye because it had a distinctive plain burgundy cover that I’d learnt to associate with the limited editions published in Oxford for use by the Folly. I opened it to the frontispiece to find the title – A Survey of Significant Locations in England and Wales by Henry Boatright. Published in 1907, it was a vestigium survey of Earthworks and Ancient Monuments with, where possible, a compendium of any information gathered by reputable practitioners about said sites. I checked the entry for Northern Herefordshire and found listings for Croft Ambrey, Brandon Hill, Pyon Wood Camp and the battlefield at Mortimer’s Cross.

Boatright had diligently noted his impressions of possible vestigia as he examined the locations. But, being from the last century, he had yet to take up the ultramodern Yap scale of magical influence.

Should have got yourself a ghost-hunting dog, I thought. That’s the way us go-ahead twenty-first-century practitioners calibrate our science experiments.

Boatright was an unspeakably dull writer but, hopefully, conscientious – he certainly went on at length about his sense impressions in a manner that would have made Henry James proud. I did The Turn of the Screw for GCSE English, in case you wondered. And I’ve got to say, I preferred the metaphysical poets – so there.

But Boatright certainly loved Pyon Wood Camp, which was situated the other side of the road from Croft Ambrey – talking about its numinous quality and air of ancient solemnity. He also rated Croft Ambrey because of its lofty aspect, but was disappointed because he found nothing that would verify his theory that this was where Caratacus made his last stand against the Romans. Brandon Hill gave him a weak feeling in his bowels which he later attributed to some dodgy boiled beef he’d eaten the night before. I skipped Mortimer’s Cross because it was on the other side of the Lugg and, judging by Beverley’s face-off with the unicorn, whatever was running around on the ridge didn’t like to cross the river. Why that might be was something I planned to get Beverley to find out.