From the first I never had the slightest doubt that Yasser Arafat, in whose body Swiss scientists found lethally high levels of radioactive polonium earlier this month, was assassinated.

It was a matter of simple logic. On the way back from his funeral I and Jamal Zahalka, a Knesset member for the Arab Balad party and a doctoral pharmacist, came to the same conclusion - the Swiss experts' findings merely confirm my conviction.

People don't just die for no reason. I visited Arafat a few weeks before his death, and he seemed in reasonable health.

When he suddenly became very ill there was no obvious cause. The doctors at the French military hospital where he died found no explanation for his condition, nothing.

That alone was strange. Arafat was the leader of his people, a de facto head of state. The French doctors would have left no stone unturned to find a cause of death.

This left two potential causes which they might still have missed - radiation or poison. Why was poison not detected at the autopsy?

Well, to detect poison you need to know what you're looking for. The list of poisons is almost unlimited and the routine search is restricted to only a few of them.

Arafat's body was not examined for radioactive polonium.

Who had the opportunity to administer poison?

Almost anyone. During my many visits to Arafat I was always taken aback by the lax security precautions.

When I first met him in besieged Beirut I wondered at the trust he put in me. Dozens of Mossad agents and Phalangist spies were combing the city for him. How did he know I was not a Mossad agent myself, or had not been followed, or was not unwittingly carrying some location device?

In the Ramallah Mukata'a or "compound" no security measures were added. I had meals with him several times and wondered again at his openness.

US and other foreign guests who were or seemed pro-Palestinian were invited by him freely, sat next to him and could easily have slipped poison into his food.

And certain poisons don't even need food - slight physical contact is enough.

Yet this was one of the most threatened people in the world. He had many deadly enemies. Half a dozen secret services were bent on his destruction.

How could he be so lax? When I remonstrated with him he told me he believed in divine protection.

Once, when flying in a private jet from Chad to Libya, the pilot announced that the fuel had run out. He was going to crash-land in the middle of the desert.

Arafat's bodyguards covered him with cushions and formed a ring around him. They were killed, but he survived almost without a scratch.

After that he became even more fatalistic, believing that God had entrusted him with the task of liberating the Palestinian people.

So, who carried out the assassination? For me there can be no real doubt. Many had a motive, but one man had the means and a profound and lasting hatred for him - Ariel Sharon.

Sharon was furious when Arafat slipped through his fingers in Beirut. Here was his quarry, so near yet so far.

The Arab-US diplomat Philip Habib managed to strike a deal for the Palestine Liberation Organisation fighters to withdraw from the city with honour and carrying their arms. I was lying on the roof of a warehouse in Beirut harbour when the PLO troops drove past to their ships.

After that Sharon made no secret of his determination to kill Arafat. I knew Sharon well. When he resolved to do something, he never gave up.

Twice when I felt Sharon was nearing his goal I went with my wife Rachel and some colleagues to the Mukata'a to act as a human shield. Later we had the satisfaction of reading an interview with Sharon in which he complained he had not been able to carry out a planned assassination because "some Israelis were staying there."

It was more than a personal vendetta. He - and not just he - saw it as a national aim.

For many Israelis Arafat was the embodiment of the Palestinian people, an object of abysmal hatred.

It was Arafat who had resurrected the modern Palestinian national movement, the aim of which was to thwart the zionist dream of taking possession of all the land between Jordan and the sea. It was he who had led the armed struggle, the "terrorism."

And when he turned towards a peaceful settlement, recognising the state of Israel and the Oslo accords, he was even more hated. Peace was bound to give territory back to the Arabs, and what could be worse?

For years an entire army of paid propaganda hacks conducted a relentless demonisation campaign against him. Every conceivable accusation was thrown at him - even that he had Aids in order to mobilise homophobic prejudices. The French doctors, needless to say, found no trace of Aids.

Is the Israeli government capable of deciding to carry out an assassination? Well, that's an established fact.

In September 1997 an Israeli hit squad was sent to Amman to kill Khalid Mishal, the Hamas leader. The chosen instrument was levofentanyl, a deadly poison which can lead to a heart attack and other symptoms but leaves no traces. It was administered by a slight physical touch.

The act was bungled. The killers were detected by passersby and fled into the Israeli embassy, where they were besieged.

King Hussein, generally an Israeli collaborator, was furious. He threatened to hang the perpetrators unless a life-saving antidote was provided at once.

Benjamin Netanyahu, PM then as now, caved in and sent the head of Mossad to Amman with the required medicine. Mishal recovered.

In 2010 another squad was sent to assassinate Hamas operative Mahmoud al-Mabhouh in Dubai. They bungled the job too - they succeeded in killing their prey by paralysing and suffocating him, but were filmed on the hotel cameras and their identity was disclosed.

God knows how many un-bungled murders have been carried out.

Israel isn't alone in the field of course. Radioactive polonium is familiar from the means by which Alexander Litvinenko was killed in London, presumably on Vladimir Putin's orders. One must assume that every self-respecting secret service has such means of murder.

Sharon didn't kill Arafat earlier because the US was afraid that if Israel was seen to do it the region would explode against the US.

George W Bush forbade it. The answer was to do it in a way that could not be traced to Israel.

Sharon was certainly devious enough to come up with a solution. A few weeks before the 1982 invasion of Lebanon, he told US secretary of state Alexander Haig about his plan.

Haig ordered him not to unless there was a credible provocation. Lo and behold, a dastardly attempt was made on the life of the Israeli ambassador in London.

This provocation was duly deemed intolerable and the war began.

Even now the Netanyahu government must strenuously deny involvement in the assassination of Arafat for fear of the Arab world's reaction.

Instead of bragging about a successful operation our propaganda machine asserts that the Swiss experts are incompetent or lying - probably they're anti-semites too - and their conclusions are wrong.

A respected Israeli professor is trotted out to say it's all nonsense. Even the good old Aids story is called out of retirement.

Sharon himself, in his endless coma, cannot react. But his old cronies, all of them seasoned liars, repeat their stories.

Arafat was the man who was ready to make peace, and who could have got the Palestinian people to accept a deal. He also laid down the terms - a Palestinian state with borders based on the Green Line, with its capital in east Jerusalem.

This is exactly what his assassins aimed to prevent.

Uri Avnery is a former member of the Knesset and a founder of Israeli peace movement Gush Shalom. He blogs at www.avnery-news.co.il