After being questioned for three and a half hours by police, under caution, on Monday night, Benjamin Netanyahu has joined the three other prime ministers who were similarly interrogated while in office over the last four decades, over similar allegations.

All were suspected of receiving funds - or in Netanyahu’s case, expensive gifts - from businessmen.

In each of the three previous cases, the outcome was very different. Ehud Barak was not charged with illegally funding his 1999 election campaign after investigators failed to find sufficient evidence.

In Ariel Sharon’s case, the State Prosecutor was convinced there was enough evidence to prove in court that he and his son, Gilad, had received bribes to facilitate a joint Israeli-Greek tourism project, but the higher-ranking Attorney General decided otherwise and no charges were brought.

In Ehud Olmert’s case, the deposition of an American businessman who claimed to have passed on to Mr Olmert envelopes stuffed with dollars was so explosive that his cabinet colleagues forced him to resign even before the indictment. Ultimately he went to prison over another bribery case involving the Holyland real estate project.

None of these previous cases gives a clear indication of where the current investigation may be going. As with the previous prime ministers, it seems that Mr Netanyahu will not be denying that the “gifts” were given to him and his family members, rather that he will insist that they were just gifts, not a cover for something more criminal. And as in the previous cases, what will seal his fate will be two factors – whether the people around him cooperate with the investigators and how hard the forces of law will press the probe.

Prime ministers Barak and Sharon were both at the height of their powers during the investigation and the people around them kept silent under police questioning. Mr Olmert, however, was a lame duck, politically wounded by the dismal outcome of the Second Lebanon War. And eventually, police managed to “break” two of his closest aides who testified against him.

Politically, Mr Netanyahu right now seems impregnable and neither Attorney-General Avichai Mendelblitt and Police Inspector-General Ronny Alsheikh seem at all eager to bring down a serving prime minister who appointed them. However, there are rumours of at least one former close friend and another aide cooperating with the investigators. And on top of all the allegations already known to the public, there is another secret investigation, its details unbelievably not yet somehow leaked to the media, which could be the most damning.

This is not, of course, the first time Mr Netanyahu has found himself facing the investigators. Back in the late 1990s, he was the subject of two investigations – in one he was suspected of being part of a conspiracy to appoint an attorney-general as part of a political deal; in the other of having received services from a private contractor that could have been bribes. He escaped narrowly in both cases after then attorney general (and now deputy president of the Supreme Court) Elyakim Rubinstein ruled there was insufficient evidence.

It is impossible to gauge at this point the probability of an indictment. One thing is for certain, the prime minister will hold tight through the questionings, the leaks and the various recommendations until the attorney-general has his last word. Based on previous experience, that could take years. Meanwhile, he’s going nowhere and has not even appointed a deputy in the unthinkable eventuality that he may be forced out of office.