P R E
P R E S T
P R E S T E L
E S T E L
T E L
That's what the logo looked like. But in colour. If you had a colour television.
Prestel was the Viewdata service run by British Telecom. It provided very similar information to that found on teletext but, being Viewdata, was more interactive - you could enter your name and address if you wanted to be sent a holiday brochure, rather than having to phone.
Prestel was also the reason most early UK modem users learnt to hate 1200/75 modems, as V23bis was the modem standard at which the service ran. In an early parallel to ADSL, incoming data arrived at a lightning fast 1200 bps. However, you could only send data to the service at 75 bps.