The car park of a remote Berkshire retail park doubles as both meeting point and briefing location for an assignment so secretive that, even upon arrival, I still have no idea where we are going.

“OK everyone,” says Craig*, who is taking the lead on this particular operation. “Paul, you stay in the car park at the exit when we arrive to ensure nobody leaves. Elaine, you get a list of everyone on site. Beverley, you already know the layout. Can you also keep an eye on the lake and cafe? Here are photographs of the four people we will be looking for. Is everyone clear?” The purposeful nods provide their answer and, with that, the cars depart in convoy.

My instructions are definite. No Twitter postings about where we are going. No telling any third party what I am doing and do not, under any circumstances, say or write anything that will identify the people I am with. It is the first time that UK Anti-Doping has allowed a journalist to witness the inner workings of a test and the rationale for the secrecy is simple: no athlete should have any prior notification.

As we draw up to the security gates, a large sign at least puts me out of my suspense. ‘Redgrave-Pinsent Rowing Lake’, it says, adjacent to another sign that confirms we have entered British Rowing’s national training centre. It is 11am and everywhere you look are tall and extremely powerful-looking Olympic hopefuls.