I am lying on my back and trapped in a gleaming white tunnel, the surface barely six inches from my nose. There is a strange mechanical rumbling in the background, and I hear footsteps padding around the room beyond. In my mounting claustrophobia, I ask myself why I am here – but there is no way out now. A few moments later, the light dims, and as the man speaks, my thoughts begin to fade.

“The engineer has developed a way of taking control of your thoughts from the inside. He does this because he is fascinated by mind control, and wants to apply the most direct method of controlling your thoughts. He is doing this to advance his research into mind control. You will soon be aware of the engineer inserting his thoughts.”

A strange serenity descends as I realise that soon, my will won’t be my own. Then the experiment begins. I am about to be possessed.

The man who will soon take control of my thoughts is Eamonn Walsh, a psychologist who uses hypnosis to investigate psychoses at the Institute of Psychiatry in London. The idea is to turn healthy subjects into ‘virtual patients’ suffering full-on delusions, such as being possessed by a paranormal entity, allowing the scientists to understand the underlying illness in a new way, and potentially find treatments

The scientists are understandably keen to distance themselves from stage hypnotists. “It’s not flaky, it’s not for entertainment – we’ve got carefully specific research goals,” says Mitul Mehta, who collaborates with Walsh on these studies. It’s a bold idea, but can it possibly work? And what does it feel like to lose total control of your mind?