During my career I have co-written several books on computer software, worked as a software engineer, and set up and sold two small technology businesses. But in April 1999 I developed tonsillitis with its usual malaise and fatigue. I naturally assumed I would be back to health fairly quickly, but, although the tonsillitis cleared, the malaise and low energy levels persisted. I felt like I was running on fumes. I had no idea why. Then my health deteriorated further.

Months passed, then a year, and now 12 years. I have occasional periods when I’m bed bound, and I am often house bound. I’m always exhausted. I often move around at home like a frail, unstable, elderly man—at the age of 38. It’s certainly made worse by my not knowing what is causing it.

My general practitioner, and many books, suggested the illness was in some way psychosomatic (“yuppie flu,” not a proper illness). I knew in myself this wasn’t true, but there was a nagging doubt. Maybe …