Ok, I was the Tower supervisor who got the call from LTCC about the MAU 340 returning. I was told exactly what the crew had said was wrong, the fact it was over MID burning off fuel, and was requesting 27R as it was the longest runway (by 300m). I decided that as it would be fast, heavy and that he requested an extra 300m that I would put on a Full Emergency. As we know in the tower, this has implications on the positioning of fire and ambulance units all over Greater London and Thames Valley, and is NOT something we do lightly. I thought my decision justified when word came through that he had declared a PAN.
I wasn't actually the person who eventually made the Full Emergency call, as I had been given a break by then, but my successor agreed with what I had planned.
We've been burnt (pun not intended) before by crews not telling us the whole story of any problems they're having regarding a possible emergency, and I don't think we (or any emergency services - who are just following local emergency orders) should be criticised for any perceived over-reaction when we know what has happened in the past.