This is from the Pale Ale entry:
"The success of IPA in the colonial trade led to a demand for a beer of similar colour and character in Britain. IPA, with its heavy hopping, was considered too bitter for the domestic market and brewers responded with a beer called pale ale that was lower in both alcohol and hops"
It's a brave man who tries to split apart IPA and Pale Ale like that. Brewers used the two terms pretty randomly in the 19th century. Bass's IPA was officially called Pale Ale. Other brewers changed the name from IPA to Pale Ale without changing the beer. I can only see one way of truly differentiating IPA from Pale Ale: by reserving it for beers that were actually shipped to India.
Of course a beer for the domestic British market would be more lightly hopped. but not because it was too bitter for the British market. It didn't need as many hops because it was going to be drunk more quickly. It's a huge mistake to extrpolate modern practice backwards and assume hopping rates were all about flavour. They weren't. It was about beer preservation. Export versions were always more heavily hopped than domestic ones.
Domestic Pale Ales often had a higher OG than export IPA. Though the ABV was lower because they weren't as attenuated out as far for home use.
"From the early years of the 20th century , bitter began to overtake pale ale in popularity and as as result pale ale became maiinly a bottled product. A true pale ale should be different to a bitter, identical to an IPA in colour and brewed without the addition of coloured malts."
There's the only one person I know who thinks Bitter and Pale Ale are separate styles. They aren't, despite his best efforts. Bitter and Pale Ale were used interchangeably in the 19th century. I've come across dozens of articles and books where the two are used as synonyms.
I think he considers Bitter to be the running ale version of Pale Ale. The terms are really Stock Pale Ale and Running Pale Ale. But the difference in the 19th century between those two wasn't the use of coloured malts. You don't really see that in any sort of Pale Ale until after WW I and not commonly until after WW II. The real difference between Running and Stock Pale Ales was the method of conditioning.
Stock Pale Ales were put into casks and matured for months before sale. They often weren't fined but fell spontaneously bright during the long secondary conditioning. Running Pale Ales were primed and fined on racking to get them into condition and bright in just a couple of days. Running Pale Ales were generally lower gravity. They were more lightly hopped because they were going to be consumed more quickly.
Stock Pale Ales went out of fashion at the end of the 19th century and by the 1920's about the only examples remaining were a few Burton beers, like Bass Red Triangle and Worthington White Shield. Note that these were bottled beers. I'm not sure draught Stock Pale ale made it past WW I. I don't know of any true Stock Pale Ale that has been brewed in the last 40 years. To try to maintain that they live on in the form of "Pale Ale" is ludicrous.
There's a reason why the draught version tends to be called Bitter and the bottled one Pale Ale (thought this isn't always true. I've found plenty of labels that say "Bitter".) Punters in pubs used the simpler term Bitter, even though the official brewery name was Pale Ale. In the days before pump clips, there was nothing to prompt customers to use the term Pale Ale. With bottled beer, however, brewers got to pick the name they put on the label. Bitter is very rare as a brewhouse name before WW II. Pale Ale is common as muck, mostly used for beers that were marketed as Bitter.
This excerpt from a parliamentary report explains Running and Stock beers (for those who don't follow embedded links) better than I can.
Next time I'll be looking at the Bitter entry.