To all those computer hackers exulting in pizza-encrusted bedrooms across central Europe — the US presidential election was influenced! The CIA said so! — I would say this: yes, yes, perhaps. But listen: when it comes to altering the course of history through hacking, Britain is waaaay ahead.

Indeed, if you want to hear about intercepted communications properly changing the world, there is one incident in particular, 100 years ago this week, that had a much more seismic effect.