It's ridiculous and I mostly walk through it. The only time I ride is when there is no-one else in there, and even then at a fairly slow speed. It's about common sense, but unfortunately lots of people who cycle through it don't exercise theirs (if indeed they have it).
The other day one guy (exiting the lift after having come down) started shouting at another (entering the lift to go up) because he had the temerity to turn his bike around outside the lift, thus blocking the man emerging from it from cycling off down the tunnel. I almost said something along the lines of 'you shouldn't be cycling down here anyway' but then realised there's absolutely no point.
The sad thing is that I'd say 8/10 cyclists cycle through rather than walking. If I hear one coming I move over ever so slightly to the middle (assuming there are no pedestrians coming the opposite way) so they have to slow down, sometimes even stop, just to get around me. I have been glared at often, but no-one has said anything yet. Not sure how I will react when they do. I know an eye for an eye makes the whole world blind, but it's just so much fun