Accents of English can be either rhotic or non-rhotic. A rhotic accent generally has /r/ more or less whenever it appears in the spelling. A non-rhotic accent, however, does not have the /r/ in final or pre-consonantal positions What this means is that speakers of non-rhotic accents have this rule: if the in the spelling does not occur before a vowel sound, don’t pronounce it. (NOTE: vowel sound, not vowel letter.)