William Armstrong was born in Newcastle upon Tyne and grew up to be the father of hydraulics. He designed an engine that was powered by water, but nobody cared at the time. Armstrong was all about renewable energy. Back in 1863, he predicted that England would stop producing coal by 2063. He pushed for the use of solar power and hydroelectricity. He lived from 1810-1900. He has nothing to do with beer, but he is one of my personal heroes.
Before Mr. Armstrong lived Joseph Bramah, another one of my personal heroes. He is also considered a founding father of hydraulics. He patented the idea of a beer engine in 1785 and it was actually built in 1797. The dude lived in Yorkshire, England, which is where Wyeast's 1469 Private Collection Yorkshire Ale comes from.
Cask beer is unfiltered and unpasteurized. Unlike kegged beers, which are generally filtered and usually pasteurized, cask beers will continue conditioning the beer in the cask (a true secondary fermentation) due to yeast present in the final product. The effect is a softer, gentle sort of carbonation that some will argue results in a better tasting drink with more character than your lame-o standard keg beer. True cask beer (aka "Real Ale") is always served without being pushed by gas, instead being manually pulled up from the cellar with a beer engine. This is the traditional way of serving beer in England.
Some folks have the idea in their heads that real ale is naturally "warm and flat". It is severely improper to assume that a cask ale is naturally warm and flat. A proper cask ale is ideally served between 54-56 degrees, which is cool, but not cold. The natural carbonation evolved from secondary fermentation in the cask should be plainly noticeable.
As a homebrewer, you may be wondering how you might do this at home. First, consider brewing The Innkeeper and be sure to pick up a copy of the book "Cellarmanship" by Patrick O'Neill.