A man completely paralysed from the waist down after his spinal cord was sliced in half in a stabbing attack is able to walk again after undergoing pioneering surgery.
The 38-year-old Bulgarian patient, who suffered his injury in 2010, is believed to be the first person in the world to recover from complete severing of the spinal nerves.
Darek Fidyka can now walk with a frame and has been able to resume an independent life, even to the extent of driving a car. Sensation has returned to his lower limbs.
Surgeons used nerve-supporting cells from Darek's nose to provide pathways along which the broken tissue was able to grow.
Despite success in the laboratory, it is the first time the procedure has been shown to work in a human patient.
Professor Geoffrey Raisman, whose team at University College London's Institute of Neurology discovered the technique, claimed the breakthrough was "more impressive than man walking on the Moon".
"We believe that this procedure is the breakthrough which, as it is further developed, will result in a historic change in the currently hopeless outlook for people disabled by spinal cord injury," Professor Raisman said.
The research, funded by the Nicholls Spinal Injury Foundation (NSIF) and the UK Stem Cell Foundation, is featured in a special Panorama programme on BBC One tonight.
A Polish team led by one of the world's top spinal repair experts, Dr Pawel Tabakow, from Wroclaw Medical University, performed the surgery.
The procedure involved transplanting olfactory ensheathing cells (OECs) from the nose to the spinal cord.
OECs assist the repair of damaged nerves that transmit smell messages by opening up pathways for them to the olfactory bulbs in the forebrain.
Re-located to the spinal cord, they appear to enable the ends of severed nerve fibres to grow and join together - something that was previously thought to be impossible.
While some patients with partial spinal injury have made remarkable recoveries, a complete break is generally assumed to be unrepairable.
Prof Raisman said: "The observed wisdom is that the central nervous system cannot regenerate damaged connections. I've never believed that.
"Nerve fibres are trying to regenerate all the time. But there are two problems - crash barriers, which are scars, and a great big hole in the road. In order for the nerve fibres to express that ability they've always had to repair themselves, first the scar has to be opened up, and then you have to provide a channel that will lead them where they need to go."
He stressed that what had been achieved was a leap forward beyond promoting "plasticity" - the re-wiring of remaining connections.
Prof Raisman compared plasticity with motorists finding other routes around a closed section of road.
"Imagine that part of the M1 motorway from London to Edinburgh has been washed away by the River Trent in the Midlands," he said.
"Cars will eventually find their way through the B roads and country roads - that's plasticity. Clearly it's never going to be as efficient as using the motorway. What we're doing is repairing the motorway, and it's the first time this has been achieved.
"What the procedure does is provide a bridge that enables cut nerve fibres to grow across a gap. The cells open up a door on either side of the broken tissue and create a pathway for the nerves to follow."
He said team was convinced that Darek's recovery was due to the procedure, and not spontaneous repair through hidden residual nerve connections.
"The patient is now able to move around the hips and on the left side he's experienced considerable recovery of the leg muscles," said Prof Raisman.
"He can get around with a walker and he's been able to resume much of his original life, including driving a car.
"He's not dancing, but he's absolutely delighted."
The professor added: "If we can raise the funding we hope to see at least three more patients treated in Poland over the next three to five years. The hope is that this will sufficiently convince other neurosurgeons.
"The number of patients who are completely paralysed is enormous. There are millions of them in the world. If we can convince the global neurosurgeon community that this works then it will develop very rapidly indeed."
David Nicholls, founder of NSIF, whose son Daniel was paralysed in a spinal injury accident in 2003, said: "Paralysis is something that most of us don't know very much about, because we are not affected by it. One of the most devastating moments a parent will ever experience is the sight of their son or daughter lying motionless in bed and facing the reality that they may never walk again.
"The scientific information relating to this significant advancement will be made available to other researchers around the world so that together we can fight to finally find a cure for this condition which robs people of their lives."