Andy Murray calls it "draconian". Rafael Nadal says it makes him "feel like a criminal". To anti-doping agencies around the world it's the most important weapon they have.
This is the "whereabouts" system, and I'm about to join it.
On Wednesday afternoon I was officially added to something called the National Registered Testing Pool, the first non-sportsman ever to be given such access. From now on I have to specify where I'll be for an hour a day, seven days a week, for up to three months in advance.
Why? So I am available for random out-of-competition tests. Why me? Because this is exactly what the 400 or so elite Olympians in Britain have to do, because it is the controversial heart of the fight against doping and because I want to see exactly how easy or onerous it is to stay on the right side of the system.