In ONE crucial respect, the spy trade is different from almost every other business on earth. Its successes – an enemy agent turned, a disaster averted by skilled intelligence gathering – are by definition secret. When we learn of them, it is often years later. Of things which did not happen, we may never learn at all. So when an intelligence agency starts making headlines, it's usually because of a failure.

That principle holds good once again in the increasingly lurid affair of Mahmoud al-Mabhouh.

Yes, in narrow terms, the operation was a success. A targeted assassination had been carried out, a senior figure in a group committed to the destruction of the state of Israel had been eliminated. But the gains are surely outweighed by the losses: international uproar, the straining of relations with important allies, further evidence that Israel behaves as madly or worse than its enemies. Of course, the hubbub will fade. But would Israel have preferred the whole thing had passed without much notice, as it seemed set to do? You bet.

That is, of course, if it was Mossad. James Jesus Angleton, the brilliant but paranoid head of CIA counter-intelligence, used to talk about the "wilderness of mirrors" in the spying trade that could drive a man close to madness.

In the Middle East, the mirrors are different, but the wilderness they create is no less disorienting. Was it Mossad? Or was it foes of Israel who deliberately made it look like the agency's work, in order to discredit Israel. But then again could the legendarily efficient Mossad really have left so many clues? To which the answer is yes, if you subscribe to the cock-up theory of life. Or were the Israelis quietly working with the Fatah movement, Hamas' rival for control of Palestine, on the basis of my enemy's enemy is my friend? Or – a thesis supported by the absence of his usual retinue of bodyguards – was al-Mabhouh the victim of an internal Hamas power struggle, in which Israel was set up to take the blame?