Mighty mouse please may I ask?
At what "fuel endurence remaining time" do your "company procedures" require you to confess your combined judgements were incorrect and require a full Mayday call to the Heathrow director and to which airport will you proceed. Destination or alternate or nearest suitable or any?
If this is not actually written down, then your companies intent, by ommision, could be, to have your judgement which had already been proven wrong on your fuel load, again regarded as wrong as you obviously delayed too long the mayday call, and the whole crash was yours and "pilot error."
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We will do the drill according to the amendments to the amendments I er think?