Can the UK Home Secretary order Ofcom to ignore its own legal duties? A court case that effectively began with the trial of a GSM gateway operator will soon decide the answer to that difficult, and potentially expensive, question.

Years ago, there was a growing market for cheap overseas phone calls. Readers who are grey of beard and long of memory will remember the adverts for these phone numbers: you'd call the gateway number before dialling the country of your choice. Your call would then be forwarded without paying the eye-wateringly high per-minute rates demanded by telcos back in the early 2000s.

The piece of equipment crucial to these companies was a GSM gateway. Effectively a giant phone with hundreds of SIM cards, these gateways took advantage of mobile phone companies' overseas calling deals to forward domestic calls onwards, neatly working around telcos' billing departments. Think of them like a VPN for voice calls and SMS messages.