Over the course of the 20th century this monolingual population all but disappeared, but a small percentage remained at the time of the 1981 census. Most Welsh-speaking people in Wales also speak English. However, many Welsh-speaking people are more comfortable expressing themselves in Welsh than in English. A speaker's choice of language can vary according to the subject domain and the social context, even within a single discourse (known in linguistics as code-switching). Welsh speakers are largely concentrated in the north and west of Wales, principally , Conwy County Borough, Denbighshire, Anglesey, Carmarthenshire, north Pembrokeshire, Ceredigion, parts of Glamorgan, and north-west and extreme south-west . However, first-language and other fluent speakers can be found throughout Wales. Outside Wales The rest of the UK Welsh-speaking communities persisted well into the modern period across the border in England. Archenfield was still Welsh enough in the time of Elizabeth I for the Bishop of Hereford to be made responsible, together with the four Welsh bishops, for the translation of the Bible and the Book of Common Prayer into Welsh. Welsh was still commonly spoken there in the first half of the 19th century, and churchwardens' notices were put up in both Welsh and English until about 1860. Alexander John Ellis in the 1880s identified a small part of Shropshire as still then speaking Welsh, with the "Celtic Border" passing from Llanymynech through Oswestry to Chirk. The number of Welsh-speaking people in the rest of Britain has not yet been counted for statistical purposes. In 1993, the Welsh-language television channel S4C published the results of a survey into the numbers of people who spoke or understood Welsh, which estimated that there were around 133,000 Welsh-speaking people living in England, about 50,000 of them in the Greater London area. The Welsh Language Board, on the basis of an analysis of the Office for National Statistics Longitudinal Study, estimated there were 110,000 Welsh-speaking people in England, and another thousand in Scotland and Northern Ireland. In the 2011 census, 8,248 people in England gave Welsh in answer to the question "What is your main language?" The Office for National Statistics subsequently published a census glossary of terms to support the release of results from the census, including their definition of "main language" as referring to "first or preferred language" (though that wording was not in the census questionnaire itself). The wards in England with the most people