It was the case of the missing PhD student. As another academic year got under way at Imperial College London, a senior professor was bemused at the absence of one of her students. He had worked in her lab for three years and had one more left to complete his studies. But he had stopped coming in.Eventually, the professor called him. He had left for a six-figure salary at Apple.“He was offered such a huge amount of money that he simply stopped everything and left,” said Maja Pantic, professor of affective and behavioural computing at Imperial. “It’s five times the salary I can offer. It’s unbelievable. We cannot compete.”