It enables both crew to keep their attention focused on the critical phase of flight called taxiing;
Good point - its a hole in the cheese whichever way you look at it
Modern performance methods and/or systems used in some other airlines are instant, they do not rely on a (London based) central performance department issuing instructions to crew scattered globally taxiing their aircraft, totally unaware of the delays it causes other operators
I know quite a few Nigels and they are very totally aware of it, believe me. My understanding is that it isn't just London based, there are, or used to be, several additional regional centres which handle BA clearances via ACARS. Are there any alternatives that are as safe? Crew operated Laptop? (think MK - Halifax). You could argue that they shouldn't push back or should push back and hold while waiting, however, but on a crowded ramp or when there is a shortage of gate space that is possibly just as bad.
I'm not a professional runway engineer so I cant say whether the signage at that turn meets international standards but I find it hard to imagine that it passes the red face test at night.