English After RP
From the Preface: “The purpose of this short book is to gather in one convenient place a description of notable ways in which contemporary standard British speech differs from the British upper class accent of the last century, Received Pronunciation (RP)… around the world, knowledge of British pronunciation is still rooted in RP: wherever I travel, I find that much of what is taught about British pronunciation is out of date.
“Many people are aware that things have changed, and a number of them have asked me to write a guide to modern developments.” More at Palgrave Macmillan