Much is known about past missions, but in recent times “secret service” has never been a more appropriate title. Reports reached the media that General Hassan Shateri, a senior member of Iran’s Revolutionary Guard, had been shot dead in either Syria or Lebanon. The state-controlled Iranian media immediately said the death was the work of “mercenaries of the Zionist regime”. The accusation was predictable from one of Israel’s sworn enemies. But five Iranian nuclear scientists have also met with grisly ends since 2007 alone, most blown up in their cars on their way to work or at their homes. A pattern has emerged – in all cases the finger of blame was pointed at Mossad.

Details occasionally come from non-Israeli sources: in 2010, Australia expelled an Israeli diplomat after a fake Australian passport was used in the killing of al-Mabhouh. An Australian security source claimed this case was key in the death of Zygier, who was apparently about to blow the whistle. Israel, never a nation to shy away from trying to control the news agenda, has always stayed silent about the circumstances surrounding the apparent suicide of its Prisoner X, as it has about the Iranians, and the  Canadian, and many other suspicious deaths.

The silence has continued. One Mossad head and another source who had been deputy head of the agency both refused to speak about any aspect of the Prisoner X case, or more generally about the workings of Mossad. Some see this tactic as a mistake – one Israeli newspaper reporter, who was until Wednesday bound by the official censor in the Zygier case, said: “I wouldn’t have been interested in the [Prisoner X] story unless the censor had been involved.”

It wasn’t always like this. Perhaps its most famous operation is Wrath of God, in which a team of operatives hunted down the members of Black September, a Palestinian terror group thought to have been responsible for killing 11 members of the Israeli team at the 1972 Olympics. The Munich operation is rare in that its key personnel have been prepared to talk about it, providing enough detail for Steven Spielberg to turn the story into a film.

In his book about the mission, which some say was still active as late as 1992, journalist Aaron Klein – who interviewed many of the agents involved – claims much of the intelligence that underpinned it was flimsy at best. The evidence against Wael Zwaiter, the first hit, was “uncorroborated and improperly cross-referenced. Looking back, his assassination was a mistake.” He concludes that the real architects of the Munich murders were shielded by Arab governments and spirited away. One aspect ommited from Spielberg’s film was the so-called Lillehammer Affair, which took place in 1973. Then, Mossad agents thought that they had tracked down Ali Hassan Salameh, who was Black September’s operations chief. The agents believed Salameh was working as a waiter in a restaurant in Norway.

In fact it was a case of mistaken identity and an innocent Moroccan called Ahmed Bouchiki was killed as he walked home from the cinema with his pregnant wife. Most members of the kill team were convicted in Norway before being sent back to Israel in 1975. But that was not the end. Salameh met his death alongside several other people when a remote controlled bomb detonated in Beirut in 1979.

One of the most controversial missions was the capture in Argentina of Adolf Eichmann, one of the main architects of the Holocaust, who was brought back to Israel, tried and hanged in 1962. Many, even in Israel, thought that chasing Eichmann to South America was not an appropriate use of Mossad’s resources and believed that it should be sticking to its primary aim: eliminating those closer to home who posed an immediate threat to Israel.

In more recent times, Mossad’s focus has indeed been more localised. In 1986, Mordechai Vanunu, a former nuclear scientist passed on details of Israel’s nuclear programme to The Sunday Times after growing to detest weapons of mass destruction.

What followed was the stuff of John le Carré – Vanunu, a Christian convert from Judaism – was lured from London to Rome by a Mossad agent, who was almost certainly acting as a honeytrap. In the Italian capital he was drugged and put on a plane to Tel Aviv. Back in Israel he was convicted and spent the next 18 years in prison, 11 in solitary confinement, and to this day has severe restrictions on what he can do.

On Zygier, the Israeli government again appears unprepared to tell the world why the once-promising spy was in prison. Given the agency’s track record, it could be some time before we know the truth.