> the hypothesis that there is no information in the past history of share prices which can be used to predict the future

A belief in that hypothesis strikes me as particularly delusional. The strongest indicator of what a share price will be at `t+1` is what the share price is at `t+0`. Why would anyone delude themselves otherwise?

Maybe that would hold true if execution prices are never revealed (not even to the participants of a trade), but prices are streamed out constantly and are exactly what traders are interested in (how else can they measure their 'gains' and 'losses'?).