I understand, but my point is that even though it seems like a limited number of desks to you because what you rightly observe is that they are not enough to absorb queues, that « limited number » is already vastly more than is needed in airports that use automated border processes for eligible foreign visitors. In other words « not enough » is by no means synonymous with « no additional » at all.

Again, it’s easy to estimate the gains by looking at countries which have installed automated border processes for far more visitors than in the uk, such as Singapore, Australia or Israel, the effects on workforce are massive, particularly when combined with pre screening through electronic authority as is the case in the uk now as it further limits the necessary checks for passports that have already been pre approved for entry.