The wind-chill temperature is -15 degrees Celcius, and Wim Hof is playing football. Topless. Though this is doubtless one of his favourite pastimes, on this occasion 'The Iceman' is participating in a medical study by Radboud University in the Netherlands, training a group of spritely young volunteers to acquire his superhuman hardiness. "You're learning to train your mind so that you're in control" explains one apprentice as he dries off after an ice-bath in a car park. "It's a powerful feeling." But the benefits of Wim's meditation techniques turn out to be much more significant than simply not needing a coat. Could they transform our approach to dealing with disease?