“We were the first centre in the world to pioneer spinal cord stimulation,” says Al-Kaisy proudly. “We try to send small bolts of electricity to the spinal cord by inserting a wire in the epidural area. It’s only one or two volts, so the patient feels just a tingling sensation over where the pain is, instead of feeling the actual pain. The patient feels nothing except his pain going down. It’s not invasive – we usually send patients home the same day.”

When Carter, the chap with the agonised groin, had failed to respond to any other treatments, Al-Kaisy tried his box of tricks. “We gave him something called a dorsal root ganglion stimulation,” says Al-Kaisy. “It makes the spine hyperexcited, and sends impulses to the spinal cord and the brain. Over ten days the intensity of pain went down by 70 per cent – by the patient’s own assessment.

“He wrote me a very nice email saying I had changed his life, that the pain had just stopped completely, and that he was coming back to normality. He said his job was saved, as was his marriage, and he wanted to go back to playing sport. This is a remarkable outcome. You cannot get it from any other therapies.”

The greatest recent breakthrough in assessing pain, according to Irene Tracey, head of the University of Oxford’s Nuffield Department of Clinical Neurosciences, has been the understanding that chronic pain is a thing in its own right. She explains: “We always thought of it as acute pain that just goes on and on – and if chronic pain is just a continuation of acute pain, let’s fix the thing that caused the acute and the chronic should go away. That has spectacularly failed. Now we think of chronic pain as a shift to another place, with different mechanisms, such as changes in genetic expression, chemical release, neurophysiology and wiring. We’ve got all these completely new ways of thinking about chronic pain. That’s the paradigm shift in the pain field.”

Tracey has been called the “Queen of Pain” by some media commentators. Despite her nickname, in person she is far from alarming: a bright-eyed, enthusiastic, welcoming and hectically fluent woman of 50, she talks about pain at a personal level. She has no problem defining the “ultimate pain” that scores 10 on the McGill Questionnaire: “I’ve been through childbirth three times, and my 10 is a very different 10 from before I had kids. I’ve got a whole new calibration on that scale.” But how does she explain the ultimate pain to people who haven’t experienced childbirth? “I say, ‘Imagine you’ve slammed your hand in a car door – that’s 10.’”

Recently, she says, there has been an explosion of understanding about how the brain is involved in pain. Neuroimaging, she explains, helps to connect the subjective pain with the objective perception of it. “It fills that space between what you can see and what’s being reported. We can plug that gap and explain why the patient is in pain even though you can’t see it on your X-ray or whatever. You’re helping to bring truth and validity to these poor people who are in pain but not believed.”

But you can’t simply “see” pain glowing and throbbing on the screen in front of you. “Brain imaging has taught us about the networks of the brain and how they work,” she says. “It’s not a pain-measuring device. It’s a tool that gives you fantastic insight into the anatomy, the physiology and the neurochemistry of your body and can tell us why you have pain, and where we should go in and try to fix it.”

Some of the ways in, she says, are remarkably direct and mechanical – like Al-Kaisy’s spinal cord stimulation wire. “There are now devices you can attach to your head and allow you to manipulate bits of the brain. You can wear them like bathing caps. They’re portable, ethically allowed brain-simulation devices. They’re easy for patients to use and evidence is coming, in clinical trials, that they are good for strokes and rehabilitation.”