To rock or not to rock?

Amongst my fellow beer nerds there has been some discussion of late on the best way to deal with cask beer in the cellar. One point of controversy has been whether casks should be rocked and rolled to give a good mix before stillaging. That's certainly what I was taught, but I don't always bother if I've had to roll the cask a considerable distance to get to the stillage.

Seeking a definitive answer to this conundrum I looked in the library at work and found The Manual of Good Practice for the use of Copper, Isinglass and Auxiliary Finings in Brewing.

I haven't had a chance to read through it all yet but skimming through I came to the following passage:

The Influence of Agitation

Reports of the optimisation of supernatant clarity with respect to agitation exist for yeast and trub, and a considerable quantity of work has been carried out on the influence of agitation on natural yeast floculation. It seems that a certain degree of agitation is beneficial or even necessary for natural yeast floculation, but that over floculation causes yeast flocs to break up. However, no work has been found on the agitated floculation of yeast in the presence of a floculating agent.

So no definitive answer yet. I suspect it's one of those questions to which the answer is "it depends".