Phileas - your recollection is incorrect I'm afraid, it's 5% of the trip fuel, or 3% if you operate in reduced contingency, or even less under other circumstances.
Etimegev - I remember MH arriving at LHR with lower levels of fuel than ideal, didn't they plan their alternate as the other runway at LHR to reduce the alternate file they needed to carry?
Paull - sounds like your carrier and the crew on the day did the right job, they took the fuel necessary, and probably more than that so that they didn't arrive at their alternate with an uncomfortable feeling. They then made sound decisions based in the information they had from ATC about the length of time it would take to make a 2nd approach. At the end of the day it is better to be in the ground somewhere where you don't want to be than in the air with nowhere left to go.