‘Oh yes,’ she said. ‘ I should think so. I’m sure I’ve read about it in the literature. And I’ve heard anecdotal reports. There was a keeper who kept the filthy stuff in an old cider bottle. He came home pissed one night from the pub and drank it by mistake. There was only a little left in bottle but it killed him immediately. Served him bloody well right. Do you want me to check the details and phone you back?’

‘That would be very kind, Jane. If it’s not too much trouble.’

‘Now, George. You know that nothing is too much trouble for you.’ She giggled like a flirting adolescent and hung up.

While he waited for the pathologist to phone him back he sat in the drawing-room. The room was as cold as the freezer where he had put the dead buzzard on his return to Back Rigg. There was no fire in the grate and it had never occurred to Ursula and Fred that they might install central heating, so the kitchen was the only warm room in the house. But Molly was in the kitchen and he did not want to talk to Molly until he had all the facts straight.

Jane Mason phoned back remarkably quickly, having digested, apparently, all there was to know about the subject. George often marvelled that someone so obviously intelligent and professionally competent could make so many mistakes about birds.

‘The active chemical in phosdrin is mevinphos,’ she said. ‘ I’ve only a summary of each of the cases here but I can send you photocopies with more detailed histories if you need them.’ She paused. ‘It’s powerful stuff, George. It’s been known to kill a healthy adult within an hour.’

‘Could it be easily masked?’ he asked.

‘Quite easily. It’s an reddish orange liquid, and you need so little that it would be very hard to detect in, say, a glass of whisky or brandy.’

‘Would a pathologist be able to tell that the poison had been used?’ He held his breath as he waited for her to reply.

‘Not purely on post-mortem appearances,’ she said. ‘You know the procedure as well as I do, George. This is like telling my grandmother to suck eggs. If there was no anatomical cause of death and no specific pathological abnormality the pathologist would ask the police to consider the possibility of poison. Then tests would be done at the Forensic Science Lab in Wetherby. That’s very dramatic. They send the samples down by police car, sirens wailing.’

‘Yes,’ he said. ‘ Of course. Would the laboratory pick up the phosdrin? Even if they didn’t know what they were looking for?’