Even a Running Bitter was likely to have at least two to four weeks conditioning in the brewery. During which time you'd want the beer to fully carbonate itself. Because which pub would want flat beer? (And for my more craftily-orientated readers, cask beer is not "flat", just with a sensible level of carbonation that won't leave you as bloated as a pregnant warthog after a pint and a half.)
On the other hand, you wouldn't want your cask getting overpressurised. And that's where venting comes in.
"For this reason, if beer be left quiescent and unaerated by “rolling," at a proper storage temperature — which in England, as I have said, is somewhere about 58° — the second fermentation is easily controlled or regulated by venting; and this is much more readily accomplished by the tight peg, eased as required, than by porous pegs, which are supposed to act automatically.
Briefly described, the venting process allows of carbonic acid escaping, when in excess, without any chance of aeration by exposure, and on this principle we have a ready means of preventing flatness of beer during the colder months of the year, since if nonaeration tend to retard cask fermentation, it is evident that motion facilitating mixture of air with beer must encourage it."
"The Theory and Practice of Modern Brewing" by Frank Faulkner, 1888, page 254.
He's talking about hard and soft spiles. The former being a solid piece of wood which completely seals the shive hole. Whereas the latter is a porous piece o wood which allows gas to escape (or enter) the cask without any human intervention.
Secondary fermentation in the cask could be a problem if the temperature was too low. And this is where rolling came in.
"Brewers frequently experience the following kind of annoyance when the normal temperature of the atmosphere tends to prevent early cask condition ; their beer racked of necessity fairly clean is immediately stacked, and, the temperature being low, no fermentation results, since the suspended yeast rapidly settles to the bottom of the cask, and remains dormant there on account of the lowness of store temperature.
Now, if we oppose this restrictive influence by the combined agency of motion and resulting aeration, we shall not only prevent the subsidence of yeast, but also bring it into vigorous vital condition, all this being easily done by a daily rolling of the beer for some little time after racking."
"The Theory and Practice of Modern Brewing" by Frank Faulkner, 1888, page 254.
Agitating the casks by rolling certainly is likely to liven the yeast up and get it eating again. Though rolling around all the casks in storage once a day is quite a lot of manual effort. Especially if there are hundreds of casks.
I've only come across one case of cask rolling. And I'm not even 100% sure that's really true. I heard that when Courage Russian Stout was being brewed in Tadcaster that it was filled into casks for secondaty fermentation. And every so often they'd kick the casks around the brewery yard to keep the fermentation going.
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The one and only time that I have had muscles, was when I was Head Barman at a London Fullers pub. So every morning bright n early, I was heaving and rolling full and pretty damned heavy kegs around the floor, deep down below. Large wooden barrels would surely have been even heavier to shift and roll than those bloody kegs were . . .
Especially when you consider that beer would typically have been delivered in barrels (36 gallons) or even hogsheads (54 gallons), not the 9-gallon casks of today. Not something that one person could handle.
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