Point Seven,
The whole reason why Mayday and PAN get such a service is because in the case of MAYDAY, life is in imminent danger and in the case of PAN, there is a case of urgency.
You as an ATCO will provide the best service to a flight which declared MAYDAY or PAN to and delay all others in order to ensure safety.
If everyone did as you suggested then you would end up with so many PAN calls per day that the whole idea would be a waste of time.
Provided that the aircraft in question landed at Stansted with 30 minutes fuel in the tanks i.e. final fuel reserve then is never a question regarding the safety of the flight.
Perhaps this Captain was considering what nobody has considered;
Arrive at LAM with Stansted as Alternate......hear from ops that not only are they holding at LAM to medium levels but there is also some holding at Stansted (the usual 20 minutes or less).
So Captain thinks.......when I divert, in book terms, I will probably have to hold at Lorel or Abbot for up to 20 minutes before making an approach and then I must land with 30 minutes fuel......thus rough figures......LAM to Lorel 5 minutes, hold 20 minutes, approach, 10 minutes plus the 30 minutes so min fuel to leave LAM is some 1hr 5 minutes fuel.
So perhaps this Captain was operating very safely. We don't know and that is the important point.
Regards,
DFC