The three years starts to run from either:
(a) the date when the medical negligence occurred.
(b) the date when you had knowledge - the "the date of knowledge".
Determining the date of knowledge is difficult and is always open to dispute. For this reason it is always safest to rely on the date when the negligence occurred and that is certainly the preference at Medical Negligence London. However, in many negligence cases there is no choice - as three years may have already run from the date on which the negligence occurred - and therefore you will have to rely on the "date of knowledge."