Over the last twenty-five years, evidence has accumulated to support this idea that mild frontal lobe damage could subtly increase artistic abilities. There are cases of acquired savant syndrome caused by fronto-temporal dementia, due to the gradual loss of neurones from the frontal lobes, rather than the sudden trauma or bleeding with which it was first associated. Functional brain imaging techniques such as SPECT (single photon emission computed tomography) show remarkable similarities between savants with fronto-temporal dementia and those with autism: in both situations there is loss of function in the frontal and temporal lobe of the brain and enhanced function in the posterior part involved in visual perception. In other words, in people with savant syndrome the front ‘inhibiting’ part of the brain appears to have less activity, allowing creative parts of the brain involved in vision unfettered activity.

Functional imaging is giving all sorts of new insights into these creative processes that would have fascinated Dahl. For example, work by Charles Lamb and colleagues at Johns Hopkins in Baltimore shows that during jazz improvisation musicians have extensive deactivation of the frontal cortex: as if this inhibiting part of the brain is switched off to allow the creative juices to flow elsewhere.

In Germany, Martin Lotza examined functional brain changes during writing. He and his co-workers showed very different patterns of activity for those who were creating a story compared with those who were just copying one down. And again the frontal lobes were intimately involved. Intriguingly, for the novice writers the visual cortex at the back of the brain was active; in contrast, for full-time creative writers it was the language centres that were more active. It is as if novices watch their stories like a film inside their heads, while full-time writers narrate it with an inner voice.

I know Dahl would have been intrigued by these imaging studies. The idea that the visual and verbal centres of the brain need to be free from inhibitions and distractions for creativity to occur resonates very much with his own experience. For Dahl to write he would sit in his little work hut every day, cosy and enclosed, ‘like being in the womb’.