Great Western Coffee Shop

I had the necessity to travel to/from Warminster today!  However, I was dismayed at the events which took place in the evening.
The 1645 ex Bristol had arrived at the correct time at Warminster at 1806, made of a two-car 153 formation.  The unit then proceeded beyond Platform 2 to the crossover but remained on the up Salisbury line.
However, 1623 ex Portsmouth was running late and so this had a knock-on effect on the return working of the aforementioned unit,  the 1818 War to Wsb.   The signaller clearly wanted the Cardiff service to take precedence.  However, by doing this, the up line was blocked by the 153 unit waiting to use the crossover.  This meant that the Up Portsmouth Service (1812 off Warminster) was held at the signal outside Warminster Station.
Once the late ex Portsmouth service arrived and departed from platform (practically full, and with a good loading from Warminster passengers), the 153 unit used the crossover....and for what?  To take onboard 1 single passenger (who must have required Dilton Marsh, since he was there when the late Pompey service departed for Westbury and beyond!)  This signalling regime meant 3 services were delayed... and for what?  One passenger?