The Registrar General creates nationwide indexes after receiving quarterly returns. These indexes are arranged by calendar quarter and give name, registration district, volume, and page number. Knowing the district name and at least an approximate year in which the birth, marriage, or death occurred will reduce the search time. Places in the index are registration districts, which are not usually the same as the actual place of birth. In rural areas, many villages and parishes belong to one district.
Large cities have many districts.
This information is useful because district boundaries changed over time. Wales 2nd edition contains nineteenth century maps and lists of districts. If the index reference cannot be found, consider sending a request to the superintendent registrar's district in England. If that request is unsuccessful, search other types of records.