The first telephone networks were tiny, connecting a handful of users in closely located buildings, with a small switchboard in between.
But it didn't take long for those networks to grow from tens of people to hundreds, then thousands.
At the same time, the local networks began to be connected together as trunk lines were set up - long distance wires connecting the towns and cities all over Britain.
The Telephone Company Ltd issued the first known telephone directory on January 15, 1880. It contained details of over 250 subscribers connected to three London exchanges.
By the time of the publication of their next directory in April, the company had more than 350 subscribers on seven London exchanges and 16 provincial exchanges in other British cities.
The first inter-city trunk telephone line was opened between Halifax and Bradford at the beginning of 1880.
The telephone system was growing fast and it was clear that there was a requirement to connect the various exchanges around the country with long distance or 'trunk' wires, linking chief cities and towns through intermediate points. This process was to take more than two decades.
Why were they called 'trunk' lines? For the same reason that main railway lines and arterial roads of the time were called that - because the network was compared to a tree with a main trunk, from which many smaller branches fanned out.
London's first trunk telephone line, linking the city with Brighton, did not open until December 1884. Until then, the government had not allowed links between different licence areas. The following year long-distance telephone trials took place between London and Liverpool. Telegraph circuits were employed connecting participants stationed in Uxbridge and Liverpool. By the end of the decade, the North and the North Midlands had a well developed trunk network.
A trunk circuit linking London to Birmingham was brought into service by the National Telephone Company on July 10, 1890. For the first time telephone communication was opened between London and what were then termed 'the Midland and Northern Counties'.
The first ever underground trunk telephone cable went from London to Birmingham. The cable from London to the west was part of the second batch of cables that were laid following that success.
The trunk network initially joined cities together, before being branched out to local networks. The Western route originally went from London to Bristol and was later extended to Plymouth. Rather like the railways it was routed via major centres on the way, such as Reading and Swindon.
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