I've always been under the impression that English Pale Ale = bottled form of ESB???
That's rather ticklish. I think it's as fictitious as Brown Ale being the bottled version of Mild. Which is bollocks.
See, ESB is, like Steam Beer, a protected name in its country of origin. Fuller's is not only the definitive ESB, it's the only beer in UK with ESB on the label, on account of trademark. So what you say can't possibly be true, at least historically. Now, spelling out Extra Special Bitter is permitted, but that still doesn't mean that the package has any bearing on what's in the package is called.
Moreover, in places where the name is not protected by trademark, like USA, breweries don't confuse the consumer by calling the same beer Pale Ale or ESB whether it's in bottle or on draught. At least, they don't if they're not utterly brain dead. Consumers are fickle as well as rather like sheep. You have to keep things simple, give them a shiny great sign, or they get confused. Yes, even quality beer aficionados.
Further, all ESB is English Pale Ale, but not all English Pale Ale is ESB. There's Bitter (Ordinary, Special & Extra Special), Pale Ale, and Fuller's ESB.
Finally, Pale Ale as a reference or adjective came first, before any of the style names. In the mid to late 18th Century, coke became the fuel of choice for British maltsters. This permitted lighter malts to be malted, malts which were significantly
paler than the brown and amber malts theretofore produced. Beers produced from this new pale malt were noticeably lighter in color than previous beers. It wasn't long before brewers were touting the excellence of their pale ales in advertising.
The new pale ales were also quite bitter, at least in comparison with the other ales of that time, like Porter, Mild and Stock ale.* By the mid-19th century, the terms 'pale ale' and 'bitter' were used interchangeably by the drinking public. There was a trend in the late 20th century to call cask, draught beer Bitter and the same beer in the bottle Pale Ale, but that has since receded to calling both packages Bitter. This phenomenon was never, to the best of my knowledge, applied to Fuller's ESB, and had no effect in the USA's brewing community at all. In fact, the current trend in UK beer packaging indicates that the use of 'Pale Ale' is dropping off considerably. Sam Smith's, Bass - they still use the words 'Pale Ale' on their product, but those products are considerably different than the Bitter brewed by them.
Anyway, that's about it. Pale Ale does
not = bottled ESB.
Cheers!
Bob
* Please keep in mind that the historical beers bear little to no resemblance to what we know today as Porter and Mild.