This is from the Leicester University Historic Directories site:
In Britain the first recognisable directories emerged during the late seventeenth century, meeting a growing demand for accurate information about trade and industry.
Why was there such a demand? The answer lies in the expansion of commerce during the period. There was an increasing number of tradesmen, many of whom were becoming more specialised and forging business links.
Early directories appear to have followed two paths of development:
1.Some early directories were speculative ventures. These were established by entrepreneurial publishers in response to the expansion of trade.
2.Other directories evolved from the lists of traders kept by the earliest registry offices. This type of directory was particularly common in provincial towns.
Directory publishers during this early period came from all lines of work, which gave them access to information about names and addresses. Some typical examples include:
The ways in which publishers collected data also varied considerably. Some obtained information by personal canvassing and combined the results with existing listings.
Other publishers simply asked people to send in their names together with a small payment if they wanted to be included in the directory.
Wider geographical coverage
Another important development was the emergence of larger-scale directories during the late eighteenth century. These covered substantial parts of the country, in contrast to previous directories which had focussed upon a single town and its surroundings.
Such ambitious publications were costly to produce, requiring collection of data by a large number of local agents. Consequently the production of these national and provincial directories was increasingly concentrated into the hands of a few large companies.
The Post Office
By the early nineteenth century methods of compilation had become more organised. In part, this reflected the growing links between directories and the Post Office. Many postal officials, such as Frederick Kelly, turned their hand to directory publishing as a means of both aiding their work and making some extra money. Information was collected by letter carriers, who circulated forms during their postal rounds, and also delivered the finished directory on commission.