‘Who could have administered—?’

‘Hold your horses, Craig. Despite this, I am still leaning towards the accidental rather than the deliberate, principally for the obvious reason that despite being such a deadly poison, it did not kill her. A poisoner would have been quite incompetent to have failed to do so, given how little is required to do the job.’

‘So what are you saying?’

‘Let’s stick to the facts. Mrs Roy seemed to be exposed to a tiny but gradual accumulation over at least nine months. Indeed, my examination of her kidneys correlates with this quite well. It shows she had been excreting the poison quite successfully for many weeks if not months. Stool samples I took from the cadaver were a further confirmation.’

‘So what are the possibilities, doctor?’

‘Initially I had thought that she might have sampled a supplier ingredient, perhaps an imported spice offered to her company, which might have been contaminated with a basic rat poison. But that doesn’t quite work with the gradual nature of the poisoning, and thank goodness, because she would not have been the only victim. So I would say it is one of two things. First, there is mention in her records that Mrs Roy was self-medicating with herbal remedies. There is no knowing what is in some quack medicines, particularly if they were acquired in an unregulated marketplace. So that would be my first suspicion. Alternatively, it could be a contaminated batch of illegal narcotics such as cocaine. I didn’t find any evidence of cocaine in her body, but that isn’t surprising. It is metabolised quite quickly, and is undetectable after four days.’

‘What if it was deliberate?’

Delahaye sucked his teeth. ‘We obviously can’t rule out a deliberate poisoning, and it would be a good choice of toxin. While pure thallium is a soft blue-grey metal, which doesn’t lend itself to being mixed with food, thallium sulphide would make rather an effective poison. It is a tasteless water-soluble salt which could easily be mixed with food. However, you’ve got to be very careful. The literature describes how it may penetrate even through rubber gloves into the skin.’

‘What did her GP make of her symptoms?’

Delahaye smiled. ‘Her doctors didn’t find thallium because they weren’t looking for it. Her kidney function tests showed problems, but it was thought to be completely separate ailment from her neurasthenia and paraesthesia. Likewise the alopecia was treated as if it was an unlinked issue. I think what they were most concerned about was her weight loss, which of course can itself cause kidney problems. But anorexia itself is yet another symptom of thallium poisoning.’

‘The flat where she stayed a couple of days a week is still sealed off, and I do remember a well-stocked bathroom cabinet. I’ll go back and have a check. And I suppose I should search her main home too.’

‘That would be a good idea,’ Delahaye said.

After ending the call, Gillard realised that this line of inquiry could not have come at a better time. With his main line forensic evidence now tainted, there was something more promising to get his detective team involved in. And finally he had some evidential justification for a more detailed look into Mrs Roy’s company. Perhaps the answer to who murdered Mrs Roy would come from within Empire of Spice Plc.