Three has stressed that "not all participants will experience the full Shine service" over the 24 hour period. That means it could come on intermittently, or only affect certain sites. "You might still see some ads on some websites, or notice some formatting errors," Three explains to trial participants. "Don't worry -- this is something we're aware of, and we're working to fix it." The technology only works on Three's own network too, so testers won't see the benefit while they're connected over Wi-Fi.

The method by which Shine blocks ads at the network level is unclear. The company says it uses "machines" that are capable of performing deep packet inspection (DPI) inside the network. Using a mixture of "real-time analysis, artificial intelligence and algorithms," the team is able to identify ads and stop them without breaking the original webpage or app.

Once the trial is over, Three will be picking a selection of customers and asking them for feedback. Responses will be gathered over the phone, however "it may take up to three months" for the company to call.

Ad blocking is a divisive subject. There are clear benefits for the customer -- better privacy and a cleaner, faster experience on the web -- but it also threatens the business model of countless internet companies. "The current ad model is broken," Tom Malleschitz, Three's chief marketing officer said in May. "It frustrates customers, eats up their data allowance and can jeopardise their privacy. Something needs to change."

While ad blocking is on the rise, it's still a niche practice -- mostly because people have to go out of their way to install an app or browser extension. If Three was to enable it by default, or offer it during the setup of every phone it sells, that could change the numbers dramatically. Three is stepping cautiously -- EE and O2, even more so -- but if it decides to go all-in with ad blocking, it could have huge implications for the internet.