No. An is used before vowel sounds, not just vowels. Ive had this corrected many times by brits. Imho, british education is much more focused on speaking english than writing it, which changes the emphasis of some rules. But it sounds strange when speaking in a non-brit accent. "An istoric" v "An historic".
Historic begins with a hard h consonant sound. The h isn't silent. "A historic" is correct.
With that said, I don't personally have a problem with "an historic." I recognize it as a convention adopted by people whose dialect favors the silent h historic.
The difference in accent in relation to the written word between the old and new world is tied to the geographic and religious histories of the two cultures. North American english strives to mirror spoken and written language, whereas the older cultures in the UK see little problem with such differences.
