Hi Airbus:
The source of the pressure? The EAT machine giving 30 minutes delay; the green haze around each of the holding stacks; introduction of TEAM (telling you there's no end in sight), questions from the aircrew "What's causing the delay"; strong wind slowing the rate etc. When its like this, if you care, you feel you cannot give more than the minimum and that creates the pressure. The fact is, the spacing matters to airport's customers and we know it.
Imagine, if there are 30 aircraft waiting to approach and you miss half a mile on the first gap then every aircraft behind is pushed back by half a mile - (that's 29 aircarft = 14.5 extra miles of total flying); miss half a mile on the second gap then the remainig 28 aircraft have to do that (that's another 14nm of flying to add to the total - 28.5nm so far...). Keep going for all 30 aircraft and the total additional flying done by all 30 aircraft in the queue is in the hundreds of miles - just for missing each gap by half a mile. Heathrow lands about 42 each hour, for about 17 hours each day. Explains why BA alone spend about $2m each month in fuel just going around the holds.
It is very easy to say there is no pressure but in reality it is inevitable. Miss the gap and every body sees it - the performance of the Final Director is visible at a glance. The only way to remove that pressure is to reduce the runway loading so that spacing is not critical.
.4