Just what is the largest 'British' records collection on Ancestry (www.ancestry.co.uk)?
In terms of records specifically drawn from across the UK, it may surprise you to know that the largest collection holds 278,407,890 records, including some records from the Republic of Ireland prior to Partition in 1921 - but it may not be a collection that you have often considered.
So here it is, and the relevant blurb from the site!
British Phone Books, 1880-1984
https://www.ancestry.co.uk/search/collections/1025/
Source: British phone books 1880-1984 from the collection held by BT Archives. Images reproduced by courtesy of BT Archives, London, England.
About British Phone Books, 1880-1984
This collection contains British phone books published between 1880, the year after the public telephone service was introduced to the UK, and 1984, from the historic phone book collection held by BT Archives. The database currently contains 1780 phone books and provides near full county coverage for England as well as containing substantial records for Scotland, Ireland, and Wales.
About Phone Books:
The largest section of the phone book, and generally the most significant for family historians, is the alphabetical listings or directory. The alphabetical listings typically contain the following details:
Surname of person (usually the head of household) or name of business
Address
Exchange (up to 1968)
Telephone Number
Phone books also contain an introduction of useful local and operational information. Located at the front of the book these pages may contain lists of abbreviations used, contact information for important government agencies, instructions on how to make long distance calls, explanations of the exchanges and their coverage, or other necessary information in order to use the phone book and telephone equipment. The introduction is not searchable and can only be seen by using the browse function.
Advertisements for local businesses occasionally appear at the tops and bottoms of the alphabetical listings pages, as well as on full separate pages designated as such. Advertisements cannot be searched independently but can be seen by selecting the image of the phone book following searching for a name in close alphabetical proximity or by using the browse function.
Why use Phone Books?
Phone books are very useful for pinpointing individuals in a particular place and time. While censuses were only conducted once every ten years, phone books were published around every one to two years, creating in essence, an almost year by year record of individuals' geographic locations and movements. This makes it possible to locate many individuals in between census years and especially to find family members during years in which censuses are not currently available to the public. For reference, the latest viewable UK census is 1901, and will remain so until early 2012 when the 1911 census can be released.
Phone books are also very telling of an individual's economic and social status since telephone ownership is a prerequisite to an individual's inclusion within this collection. Early subscribers to the telephone service were typically large businesses or the well-to-do. Telephone ownership gradually increased, reflected by a corresponding growth in the size and number of phone books, and from the second quarter of the twentieth century became more commonly adopted by domestic subscribers.
While the alphabetical listings in the phone book will likely be of most interest to researchers, if your ancestor owned a business the advertisement section might also be of interest. There you may learn the location of and type of goods and services sold or offered by the business. This may lead you to additional research in occupational records.
BT actively supports the preservation of Britain's communications heritage. BT has published its commitment in its Heritage Policy (see www.bt.com/archives) and its Connected Earth initiative enables the exploration of communications past, present and future both online (at www.connected-earth.com) and via a network of partner museums around the UK.

COMMENT: The phone books are perhaps as important a collection as trade directories for research in terms of filling in the gaps between censuses and going beyond them, but they can be seriously hard work to use. The Ancestry search page advises "Please note that in order to search these records you are required to provide a name and country/county." - you can probably add "and say a prayer" to that requirement!
Personally speaking, I rarely bother searching by name using the database, unless it is a very rare surname, as there are often far too many responses. The best bet is to try to navigate the records using the Browse This Collection section to the right of the page, where you can narrow by year range, year, and then individually browse through the titles of individual directories. Coverage varies across the UK, but Scotland and Ireland (Scotland 1896 and Dublin 1880 are the earliest) are well represented, along with England and Wales - especially London.
Well worth a look!
Chris
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