First off, there's a big difference in my mind between modern American IPAs and modern English IPAs. The BJCP style guidelines describe the flavor of an American IPA: "Hop flavor...should reflect an American or New World hop character, such as citrus, floral, pine, resinous, spicy, tropical fruit, stone fruit, berry, melon, etc...Malt flavor...is generally clean and grainy-malty although some light caramel or toasty flavors are acceptable." The guidelines for English IPA are: "The hop flavor should be similar to the aroma (floral, spicy-peppery, citrus-orange, and/or slightly grassy). Malt flavor should be...somewhat bready, optionally with light to medium-light biscuit-like, toasty, toffee-like and/or caramelly aspects."

I'm assuming you are more familiar with American IPAs than English IPAs. So, would it taste like a fresh modern American IPA, bursting with citrus, pine, and tropical fruit flavors and aroma? Not at all.

Historical IPAs brewed in England and exported to India were brewed with English hops such as East Kent Goldings, which are much more floral, herbal, and earthy compared to modern American IPA hops. After brewing they were packaged into oak barrels and shipped across the tropics, possibly undergoing a secondary fermentation from wild yeast hiding out in the barrels. The beer would likely be served at cellar temperatures or warmer with low to moderate carbonation.

Much of the hoppiness would have faded due to age, oxidation, and high temperatures after such a voyage.

The tasting notes of a homebrewed version meant to emulate the historical style describes the beer as [http://byo.com/hops/item/759-historical-india-ipa-style-profile]"more like a malty, heavy doppelbock than a mouth-tingling IPA."

I'm imagining the taste of a really old bottle of English IPA that had been poorly stored with a bit a oakiness and funk.

Sources: IPA by Mitch Steele (Stone's brewmaster) [https://beerandbrewing.com/VKHKxSsAAD6t72dF/article/a-recipe-for-historic-burton-ipa]Recipe based on Mitch Steele's research