This NTC directory lists almost every subscriber in Great Britain and Ireland in a single volume. This was posible as the yearly telephone line rental of 10 pounds was far too expensive for most people. The NTC, with about 100,000 subscribers, had a virtual monopoly in the early days of telephony. Although the Post Office owned the long-distance trunk network, it carried only two per cent of the calls at this time.
© Science Museum / Science & Society Picture Library