This post on Paul Bailey’s blog refers to the phenomenon of “top pressure”, which was widespread in the 1970s, and was described and decried at length in CAMRA publications. What this involved was delivering real ale to pubs in casks, but then connecting a cylinder of CO2 to it, and using the gas pressure to force the beer to an illuminated keg-type font on the bar.
It must have largely been a Southern phenomenon, as I don’t recall ever knowingly coming across it in the North, where a lot of the beer was real, and a lot of what wasn’t real was “tank” (which maybe merits a post of its own). In fact the only occasion when I have drunk what I believed to be top-pressure beer was in a Whitbread pub in Alton, Hampshire in about 1981. By that time the practice was in steep decline, as real ale, and the handpumps that symbolised it, were once again perceived as attractive.
The system also had a unique drawback of its own, in that not only did the gas pressure make the beer fizzy and prevent it maturing in the cask, but it also tended to disturb the sediment, so you would end up with a pint of slightly hazy pseudo-keg. Thirty years or more on, it’s hard to see why it was done, as it combined the worst of both worlds, lacking both the freshness and authenticity of cask and the consistency of genuine keg.
But, back in those days, fizzy beer that came from illuminated boxes on the bar was seen as the future, and brewers who lacked the funds to invest in kegs, kegging lines and pasteurisation facilities climbed on the bandwagon by sending out cask beer and making it masquerade as keg. How times change.