In 1978 the Post Office (now BT/British Telecom) was investing £900m a year on the telephone network, but home users were averaging only one and a half calls a day. The PO’s Research Labs had a bright idea for encouraging people to make more calls; online interaction. It was like the internet before there was an internet.

Viewdata worked like broadcast teletext, but with digital signals sent by phone line instead of broadcast. The user typed commands into a keyboard attached to a modified teletext TV set. Early modems were slow, so while viewdata received data at 1,200 bits a second, it was sent out at typing speed of 75 bps. The PO coined the trade name Prestel, and launched a service in 1979.

Prestel bombed with consumers, because hardware prices were high, subscribers had to pay for information which was often available free from teletext, and the message pages did not hold many words. A grocery chain tried using Prestel for online ordering but had to employ people in the warehouse to look at screens and hand-write the orders on paper.

In 1984, the PO had become BT and Prestel became briefly famous when a couple of computer buffs found big loopholes in its security. They gained access to the Duke of Edinburgh’s electronic mailbox and sent the messages “How are the corgies”, and “Toodle-pip”. BT was not amused and instead of thanking the hackers for exposing security loopholes, prosecuted. (Nothing changes).

In 1994 BT sold Prestel to a private company which changed the name to New Prestel, then Prestel On-Line. Modem speed had by then been doubled, but text and pictures still looked like teletext. This was good enough for the travel agents and financial institutions who still used the service, but not the new generation of PC and Internet users.

Broadcast teletext – BBC Ceefax & IBA Oracle – was simple and cheaper than dial-up Prestel, but both were swept away by the internet.