A street performer who pushed knives into his arms and walked on burning coals has helped scientists to make an advance in understanding and treating pain.
The work could lead to a safer range of pain-killing drugs.
We may dread pain, but we suffer for a reason: it warns us when we are pushing our bodies too hard, burning our fingers or drinking too much.
This helps to ensure the survival of our species.
As if to underline this, the Pakistani boy who helped a Cambridge University team discover a pain-killing genetic mutation died on his 14th birthday from injuries sustained after jumping off a roof to impress his friends.
When a British team came across the extraordinary boy they found three more related families in which there were six children — aged from two to 12 — who also felt no pain.
Each originated from the Qureshi birdari clan in northern Pakistan.
All six children with this rare inheritance appeared to be normal and had an apparently normal nervous system and normal sensations.
However, none had ever felt any pain. As a consequence, all had injuries to their lips, one requiring plastic surgery, and/or tongue caused by biting themselves in the first few years of life.
Some families were even accused of child abuse.
The carriers of the mutation also suffered frequent bruises and cuts. Most had suffered fractures which were only diagnosed in retrospect because of painless limping or lack of use of a limb. However, the older ones realised what to do in a painful situation — including acting as if in agony after football tackles.