Equity pricing: How reasonable are investors?

At the conference last year the view was expressed by Peter Gripaios that the world wide collapse of share price reflfected a "follow my leader" process which sucked in all countries, that a collallpse of the Dow Jones index was bound to affect the FT index. Insofar as the 1973 collapse on Wall street was mirrored by a huge fall in the City of London I can even provide evidence consistent with that wiew.