They didn't
drop the "h" like Cockneys, but it's true that they didn't
pronounce it - and if you are going to say "an historic event" today, then only if you don't say the "h" as in "house". "An HHistorical event" with the "h" pronounced might sound like you are a Cockney trying to be posh :-)
Some speakers do not pronounce the ‘h’ at the beginning of historic and use ‘an’ instead of ‘a’ before it. This now sounds old-fashioned.
©Oxford University Press, 2005
"The form an for the indefinite article is used before a spoken vowel sound, regardless of how the written word is spelt. If you say 'an otel' when speaking (which is now often regarded as distinctly old-fashioned), then it may be appropriate for you to write 'an hotel'; but most people say 'hotel' with a sounded 'h', and should write 'a hotel'."
http://www.askoxford.com/asktheexperts/faq/ab...