During July and August this year many quantitatively managed equity portfolio exhibited extreme volatility – initially severe weakness followed by a sharp rebound. This effect was global – occurring at first in the US, but following rapidly in the rest of the world. It is clear that the interaction of model correlation, leverage, short selling, and rapid variation in the price of risk played a major role in the evolution of returns over this volatile period. At the inaugural meeting of the London Quant Group practitioners involved in the management of quantitative equity portfolios will recount some of their experiences during this episode, and present analysis of the causes and consequences of these events.