Mordechai Vanunu, the man who exposed his country's secret nuclear weapons programme, will walk free after 18 years behind bars - most of them in harsh solitary confinement.
For nearly two decades, the Israeli authorities have been dreading the moment when Vanunu would be free to speak to the world in person about Israel's development of nuclear arms, his abduction by Mossad agents and the details of his incarceration.
The timing of his release - as the issue of weapons of mass destruction tops Washington's Middle East agenda - could not be worse.
For all these reasons, there has been plenty of speculation about whether Vanunu will be released at all. But the government has apparently conceded that attempts to incarcerate him beyond his prison sentence would be patently illegal.
None the less, the government's chief law officer officially announced in March that Vanunu still poses a major "danger to state security" - even though the information he revealed is nearly 20 years out of date.
Vanunu is therefore likely to emerge from prison into a new detention: a loose form of "house arrest" in which he will be denied the right to leave the country and will have his movements closely monitored.
The Israeli media will also be under strict orders not to interview him, even about his opinions. The ingrained self-censorship of the Israeli media on "security" matters, combined with the official system of military vetting of news, should ensure compliance.
"They say I have additional secrets but that is a lie, an excuse, a cover-up. All that was known to me has been published. Anything I can say will be a repetition"
Vanunu's crime was to reveal to the world for the first time details of Israel's nuclear weapons programme - despite government claims that Israel would not be the "first to introduce nuclear arms into the Middle East".
The revelations hugely embarrassed the American administration, which had turned a blind eye to Israel's programme.
Vanunu had accumulated his information during nine years working as a technician at the underground plant near the town of Dimona in the Negev.
According to experts, his data and photographs suggested Israel had an advanced programme that included 200 nuclear warheads.
After his story was published in 1986 in the British newspaper The Sunday Times, he was lured by Mossad agent "Cindy" to Rome where he was drugged, tied up and smuggled back to Israel.
The authorities have insisted on his completing his 18-year sentence in full and, according to his family, have imposed a crushingly strict regime on the whistleblower, which shows no sign of abating even in his last few days of captivity.
Vanunu was drugged and
captured by Mossad in Rome
Vanunu's cell measures just 2m by 3m.
For the first two and a half years of his imprisonment, a light bulb burned continuously so that he could not tell night from day. When he was briefly allowed out of the cell he was followed everywhere by guards videotaping him.
Basic rights, such as access to newspapers and TV were also denied, as were prison visits, apart from close relatives.
Amnesty International described Vanunu's ordeal as "cruel, inhuman and degrading".
In recent years, he has been allowed reading materials - although he claims in recent days they have been again withdrawn. He has also been given access to the prison yard shared with other inmates but is under strict orders not to talk to other prisoners.
In the past few weeks, there have been several reports in the Israeli media of Vanunu being disciplined after other inmates have approached him. One is reported to have even offered Vanunu a slice of cake.
In another incident in March, Vanunu was punished after he was attacked by several inmates, including Noam Federman, a supporter of the extreme right Kach party who is accused of particpating in Jewish terror attacks on Palestinians in Hebron.
Vanunu's brother, Meir, is one of the few people allowed to visit him in Shikma prison near Ashkelon. He believes Federman and others are being encouraged by the prison authorities to make Vanunu violate the terms of his detention and so provide a pretext for his continuing imprisonment.
"They are looking for an excuse not to release my brother. I warned him to be careful and keep his mouth shut"
Vanunu's brother Meir
"They are looking for an excuse not to release my brother and are making all of these tricks to not to release him," he said. "I warned him to be careful and keep his mouth shut."
According to Meir, Vanunu has lost privileges he enjoyed in the past, and is now being confined to his cell earlier.
Meir also says that when he tried to tell his brother about the recent discussions of his case by the Israeli parliament, prison guards intervened and threatened to end the visit.
Vanunu's relatives and supporters claim that the harsh prison regime imposed on him has been a form of psychological warfare designed to "break" him.
Strict solitary confinement was only partially eased seven years ago, after Vanunu's family became concerned for his mental health and threatened to demand that doctors from abroad be allowed to examine him.
Vanunu's adamant refusal to atone for his actions and his continuing commitment to a nuclear-free Israel are causing huge discomfort to security officials as he stands on the verge of freedom.
An Israeli policeman in front of
the prison near Ashkelon
If Vanunu is released on 21 April, the Israeli authorities have made it clear they will deny him the opportunity to speak to the media as far as is possible.
The man in charge of restricting Vanunu's freedoms for most of the past 18 years, Yehiel Horev, the chief security officer at the Ministry of Defence, is reported to be determined to keep Vanunu out of the spotlight forever.
In February, he recommended to the government that Vanunu be held in administrative detention - a form of arrest without trial - after he has completed his sentence.
That option was rejected on the orders of the attorney-general, who observed that it would not withstand a legal challenge.
None the less, the attorney general Menachem Mazuz has insisted that Vanunu's release "will create a significant danger to state security" and recommended that his movements should be severely circumscribed.
That assessment was based on senior defence ministry officials - assumed to be a reference to Horev.
The security services will therefore not issue Vanunu a passport, to prevent him travelling abroad, and they will track his movements and monitor his telephone calls and email traffic.
No more secrets
Vanunu himself claims through his brother not to be in the possession of any new secrets.
He says he revealed everything he knew in 1986. "They say I have additional secrets but that is a lie, an excuse, a cover-up. All that was known to me has been published. Anything I can say will be a repetition."
The Dimona atomic reactor in the
Negev desert in 2000
This was confirmed by Peter Hounam, The Sunday Times journalist who originally interviewed him. "We gathered from Vanunu every scrap of technical information about Dimona that he could remember," he said.
However, several Israeli newspapers suggested that Vanunu could still divulge two new pieces of information: the security arrangements at the Dimona plant and the names of people he worked with.
In fact, Vanunu refused to provide this information to The Sunday Times, saying he did not want to endanger his former colleagues. Moreover, it seems improbable that security arrangements at the plant have not been overhauled in the 18 years since his capture.
A different reason for Israel's continuing harassment of Vanunu was suggested by Hounam: "I think that some people are afraid that Israel might be mortified if Vanunu said how he was kidnapped."
Doubtless, the details of Vanunu's abduction may cause some embarrassment.
But a more pressing fear among security officials is the fact that Vanunu's release and his new visibility will attract unwelcome media attention to the rarely discussed issue of Israel's weapons of mass destruction programmes, including biological and chemical weapons.
"Having Vanunu running around the US and Europe talking about the bombs Israel has could be a serious irritant from the Israeli government's perspective"
"Having Vanunu running around the US and Europe talking about the bombs Israel has could be a serious irritant from the Israeli government's perspective," said Avner Cohen, an American scholar and author of Israel and the Bomb.
There is also the fear that Vanunu, a man who has resolutely stood by his principles during two decades of incarceration, may become the focal point for an anti-nuclear weapons campaign in Israel - and abroad if he is allowed to leave.
Such fears have been confirmed by senior security officials.
One was reported as saying: "He may not have any new secrets, but it is sufficient that he will mount a campaign. People around the world will use him as a banner. There is no reason for us to allow this kind of provocation when we can stop it."