Of the dozens of design decisions that TBL made during 1989, all of which continue to shape the way we build and use the web twenty-five years later, the most important was not requiring permission to link. Seems obvious now – a non-feature in fact – but it’s the reason you’re not reading this on Xanadu (or Prestel or on an X500 terminal or something). The logic of the times – embedded in those other systems – was that documents and data sources had owners and that you couldn’t just link to them without some kind of formal permission. Permission was defined as a system-to-system, technical handshake kind of thing or a person-to-person interaction, like a phone call, or, God forbid, a contract and some kind of payment. TBL’s judgement was that the community he was building his system for – the academics and engineers – wouldn’t want that and that the spontaneity of the hyperlink would trump the formality of permission. And, of course, he was right. It’s the spontaneously-created hyperlink that triggered the marvellous, unstoppable promiscuity of the World Wide Web. It explains the web’s insane rate of growth and the profusion of web services. It’s the root of all this.