Hervey’s eyes narrowed. ‘They murder sepoys, you say?’

Sleeman nodded. ‘We know it because, fearful of being found with any piece of uniform, which they certainly cannot sell, they bury their victims without stripping the body, which otherwise they always do.’

‘Damnable.’

‘And, of course, the mode of travelling on foot or on small ponies, being almost universal among those who have occasion to make long journeys whatever their rank or condition, makes the thug’s work easier. As well, the unreserved manner in which travellers of the same caste mix and communicate, and the facility with which men can feign different castes.’

Hervey, though repelled by the murder of any man in a red coat (and troubled yet by headache), was becoming impatient. ‘It appears to me to be a hopeless case.’

Somervile said that at first he’d thought the same, but was now inclined to take a less passive view – not least because thuggee was no longer confined to the native states, and the honour of the Company, and thereby the Crown, was at stake. ‘I think we might compare it with the state of England in past centuries – when highwaymen and footpads, brigands of all sorts, were not uncommon. The King’s Peace was won only by degrees.’

Hervey nodded. ‘I am not an antiquarian, but I accept the premise: a start has to be made. But with so much traffic, I cannot see how.’

Sleeman raised his hand. ‘If I may, Colonel: I believe that here, we are so to speak in England before the canals and the turnpikes. The pace of transport – of every aspect of daily life indeed – where all is carried on foot or bullock carts, provides opportunity, and likewise the assassin has little chance of being overtaken and intercepted in his operations.’

Hervey saw where this was leading, but bid him continue anyway, not least out of regard for his old friend.

‘Thuggee, Colonel, is a spider’s web of family connections, and I am convinced that this very fact will be its undoing. The strength of a web lies in its unity. Careful gathering of intelligence – in which I’ve been engaged now for a considerable time – will take apart that unity strand by strand.’

‘I understand that. Continue.’

Sleeman looked gratified at last. Five years ago, he explained, he began systematically to record every known instance of thuggee crime. This depended on the evidence of ‘approvers’ – turncoats: ‘The first point I make always to ascertain from the approver the time, place and mode of the murders as near as possible – the place whence the murdered persons came and whither they were going – and the property they had with them. On these points the approvers are always well informed. I then send to local officers of my acquaintance and have the bodies dug up before the people of the neighbouring villages, whose depositions on oath are taken down by the local authorities of the district on a form of my devising for the evidences. If the bodies are not found, the people of these villages may have seen them at the time, before their murder, and their depositions to this point will answer the purpose.’