As in so many fields of scientific endeavour following the molecular biology revo- lution, our knowledge of the role of radicals not only in pathological states, but in basic physiology has developed exponentially. Indeed, our evolving concepts have, like so many political parties, been forced into dramatic "V-turns" and contortions. Within our working lives, we have had to debate whether radicals made any con- tribution to any pathology, whilst now it is difficult not to entertain the view that every physiological process is pivotally controlled by exquisitely sensitive radical reactions....