The team at Erasmus University Medical Center, in the Netherlands, are planning human trials for what they hope is a treatment for old age. A UK scientist said the findings were "impossible to dismiss", but that unanswered questions remained. The approach works by flushing out retired or "senescent" cells in the body that have stopped dividing.

They tested it on mice that were just old (the equivalent of 90 in mouse years), those genetically programmed to age very rapidly and those aged by chemotherapy.

The findings, published in the journal Cell, showed liver function was easily restored and the animals doubled the distance they would run in a wheel.

Dr de Keizer said: "We weren't planning to look at their hair, but it was too obvious to miss.

The drug was given three times a week and the experiments have been taking place for nearly a year.