Prof Jog believes Parkinson's disease reduces the signals coming back to the brain - breaking the loop and causing the patient to freeze.

The implant his team has developed boosts that signal, enabling the patient to walk normally.

However, Prof Jog was surprised that the treatment was long-lasting and worked even when the implant was turned off.

He believes the electrical stimulus reawakens the feedback mechanism from legs to brain that is damaged by the disease.

"This is a completely different rehabilitation therapy," he said. "We had thought that the movement problems occurred in Parkinson's patients because signals from the brain to the legs were not getting through.

"But it seems that it's the signals getting back to the brain that are degraded."