Wasn't there a recent story about Heathrow closing down some 'impromptu' or 'unauthorized' muslim prayer rooms there? I wonder if that is related to this, maybe the perps were goint to 'prep' their stuff in the airport just before boarding....Creepy!!
I recall closing of a nest of unofficial (very scummy) prayer rooms in the bowels of Terminal 1 at Roissy / Charles de Gaulle in Paris.