Which all goes back to my original point about long hauls being caught out yesterday. Weather forecast CAVOK or pretty close to, nothing in the NOTAMS, middle of the afternoon lull at LHR (which is probably why they decided to carry out the de-ice/pre-ice then).
ATC only learn about delays at our TOD and the situation builds as we are the last 100 miles into LAM.
If there are sudden holds announced with 10, then 20 then 25 mins being quoted, isn't it sensible to discuss options before you use up the contigency?
Wish I worked for a company where it was considered OK to carry an hours holding fuel on every flight.
Your decision on your MAN 737 day was correct with all the information you had to hand. Yesterday was an exception.