we presently have references in the introduction that each state britain and ireland is becoming the preferred official usage nowadays it is the most favoured expression and that the term british isles should best be avoided the last quoted reference according to the guardian newspaper so it's not your mere one source as claimed despite these references however bizarrely none of these well referenced facts are to be seen in the introduction of this article canterbury tail's you ask why should it be in the lead because it is now the most favoured and preferred official alternative term lastly on a practical standpoint say for example you were looking for a new book on the types of birds wildlife in general for the region you'd be hard pressed to find any such modern books with british isles in the title why because britain and ireland has become the preferred official usage see crossley id guide britain and ireland the crossley id guides published bird atlas the breeding and wintering birds of britain and ireland british trust for ornithology etc