I wonder how much internal damage they did putting that much torque on the internal workings of that lens. They finally got smart and adjusted the focus until just the barrel in which the filter was stuck was the only thing reacting to the torque.
But then again, If Adam is doing the work and screws it up, he has enough money to purchase the lens from Norman, for replacement cost.
Amazing, he had to cut slots into the filter to remove it, which looked like a thin metal ruler. As expensive as a Canon 24-70mm lens is. I suppose you do what is necessary to remove it. I just hope that never happens to me. I do use protective filters on far less expensive lenses.
Had the same problem just a couple of days ago. Thankfully is wasn't stuck on my lens, I had it on an plastic adapter for a non OEM lens hood. No matter what I did it could get it to budge. Since this was a B& W top of the line filter, and the adapter and lens hood on cost a fraction of the protector I really needed to get it off.
Not even 2 local camera stores could remove it! A customer who happened to be at the last store suggested I apply heat and assured me it would come off. Well, I rushed home, and popped it into the toaster oven at 150 degrees, in less than a minute I started to smell plastic. I took the adapter out, the plastic was so soft that the filter fell right out undamaged, unfortunately the adapter was so soft it lost its circular shape.
Luckily it was stuck on a lens, and the adapter was only about $10 to replace.