If the New Scientist article is correct we are to believe that "many ... recipients [of the original stem cell implants] improved dramatically around three years or more after the implants" and that the new work is expected to "see an improvement in around six months to a year", with "the maximum benefits ... predicted to happen in three to five years' time".

My concern is that with such long lead times clinical trials will, if usual techniques are used, such as monitoring UPDRS scores, require decades to complete.

Once again this shows the importance of having good biomarkers. But could we ever approve a new procedure purely on the results of biomarkers, without any clinical improvement being seen?

In general I am sceptical of any work that promises that something good will happen in five years. Perhaps, as GerryW writes, "patience is required".

John