Given the following context:

A dialect of English (West Country English), known as Bristolian, Bristolese, Brizzle or Bristle (after the publication of Derek Robson's "Krek Waiters peak Bristle") is spoken by longtime residents, who are known as Bristolians. Bristol natives have a rhotic accent, in which the post-vocalic r in "car" and "card" is pronounced (unlike in Received Pronunciation). The unique feature of this accent is the "Bristol (or terminal) l", in which l is appended to words ending in a or o. Whether this is a broad l or a w is a subject of debate, with "area" pronounced "areal" or "areaw". The ending of "Bristol" is another example of the Bristol l. Bristolians pronounce -a and -o at the end of a word as -aw (cinemaw). To non-natives, the pronunciation suggests an l after the vowel.Until recently Bristolese was characterised by retention of the second-person singular, as in the doggerel "Cassn't see what bist looking at? Cassn't see as well as couldst, casst? And if couldst, 'ouldn't, 'ouldst?" The West Saxon bist is used for the English "art", and children were admonished with "Thee and thou, the Welshman's cow". In Bristolese, as in French and German, the second-person singular was not used when speaking to a superior (except by the egalitarian Quakers). The pronoun "thee" is also used in the subject position ("What bist thee doing?"), and "I" or "he" in the object position ("Give he to I."). Linguist Stanley Ellis, who found that many dialect words in the Filton area were linked to aerospace work, described Bristolese as "a cranky, crazy, crab-apple tree of language and with the sharpest, juiciest flavour that I've heard for a long time".

answer the following question:

What had Stanley Ellis heard for a long time? 

the sharpest, juiciest flavour