Sure enough, there on the yellow-painted cell wall - each an inch apart - were the figures 1 to 24 in Roman numerals. And next to the figure 24, in Hebrew, an obscenity. When this was translated into more delicate Arabic for Colonel Bassam Hamad al-Khatib, he was silent for a moment. "Can you imagine the things that happened here?" he asked. "Look, I will show you where the men were kept before torture."
We walked into a tall, high-ceilinged room, cold and damp with puddles on the floor, a stack of desks and metal cabinets hurled carelessly over the surface - but not carelessly enough to conceal a series of slightly raised lines of concrete, each line 5ft from the other.
The PLO officer knelt down and brushed aside the dust. "Several days before their departure, the Israelis smashed down all the walls of the cells here and whitewashed the walls and brought all this furniture in here to disguise the place as a storeroom. But each of these concrete lines was a low wall. There were 25 tiny cells here for prisoners in isolation and total darkness, each a bit bigger than a dog kennel. They could wait here in darkness for weeks waiting for interrogation."
Next door, in a large room of equal size with a flood of water over the floor, the Colonel paused. "Interrogations were also held here," he said. "This was a place of many beatings. The men in the cells next door could hear the screams of those being questioned. That was the point, you see: to put fear into the men about to be interrogated. They could hear their comrades screaming in the next room."
Behind us a trail of civilians entered the big room, some unsmiling young men, women in scarves and children. "They were prisoners," Colonel al- Khatib said of the men. "We are going to open this place up to all our people. We are arranging to bring parties of schoolchildren round this prison to show them what their fathers endured under the Israelis. They must know their history."
Nablus Prison No 1 - No 2 lies at the other end of the city "liberated" by the PLO-Israeli agreement last week - was built by the British, a stout white and yellow-walled fortress used by the constables of the Palestine Police to put down an earlier Arab revolt. In the hours after the Israelis left and the Palestinians ceremonially burned the Israeli flag still hanging from the top, the first Palestinian policemen made their way through the freezing, darkened corridors to explore a building which had become synonymous with fear and - according to those who spent years here - with great suffering.
The Israelis make no secret that "reasonable" (sic) force is used in interrogating Palestinians, which is a polite way of admitting torture without saying so. The late Yitzhak Rabin personally sanctioned such interrogations - to the condemnation of Amnesty International whose evidence of mistreatment and brutality in Israeli jails over the past decade runs into hundreds of pages.
But in the aftermath of the Israeli redeployment from Nablus - when western television reporters chose to emphasise the success of "peace" rather than the sinister evidence of this dark prison - only the Palestinians understood what the cells in Nablus jail represented. Only when you have walked hundreds of feet through the underground corridors, past dozens of tiny concrete cells for six men, with their single lightbulb and open lavatories, do you understand why so many Palestinians - rather than cheer - chose to hurl stones and shriek curses upon the last Israeli soldiers to leave Nablus.
Up in the former Israeli prison governor's office, General Sadi Naji, the PLO's overall commander in Nablus, is sitting in his green officer's uniform, a thin-faced man with brown, searching eyes who plays with a pile of documents on his desk as we talk. We recognised each other at once. In 1982, he was a mere captain in grubby guerrilla fatigues, fighting against the Israeli army on the Beirut perimeter, impatient with the British reporter harrying him for his views of imminent defeat. But now he was a soldier, dispassionate, anxious to prove Palestinian responsibility rather than revolution. It was as if the cells below us did not exist.
"My main problem is communications," he said. "The Israelis promised to leave everything in good order. But they stripped out most of the wiring and I have only two telephone lines... We've got to go to the people who have guns here. Those who have reason to keep these weapons, they will be given licences. Those who don't will have the guns taken from them and, if necessary, they will be put before the courts. But it was the Israelis who spread these weapons among the people during the occupation. They wanted to divide our people."
The general looks at me searchingly, to see if I understand how he feels. An exile in Egypt, Lebanon, Iraq and Syria - he spent three years in the Saddam military college in Baghdad, where there were much nastier prisons than the one in which we were sitting - he now has to keep promises made to men who were his mortal enemies. He has to forget what happened in this dreadful building - to young Palestinians whom he may yet have to confront himself, perhaps incarcerated in this very prison - in order to keep the PLO's "security" promises with Israel.
In what was once to have been the Jneid hospital - but was converted into a prison by the Israelis before it ever achieved its original purpose - there are more than 100 more cells, some with iron bunks, many more only 8ft by 4ft, without lights, in which - so more ex-prisoners said - up to four men were kept for weeks, squatting on the floor back-to-back for sleep. There was a bleak exercise yard covered in wire, a miserable room for family meetings; husbands and wives could kiss through the wire that separated them.
Here another ex-prisoner emerged. He had been 18 years in Israeli jails, including this one, for what he described as "resistance activities". Abdul Kader Sherkawi was very dark- skinned with a small moustache. "We were beaten many times; even when we complained about the beatings, we were beaten again," he said. "When we rioted, the Israelis threw tear gas into our cells. No, I won't ever forgive them - but the situation is that we must talk to them. It's the logic of peace. I deal with reality."
So does Colonel al-Khatib, back in the dank Nablus Prison No 1. Mindful of the "liberated" Israeli jails in Gaza, and the swiftness with which Yasser Arafat filled them up again with his and Israel's Palestinian opponents - one of whom died there within weeks - I could not help asking the colonel if he would ever put Palestinians inside the chilling keep which he now patrolled. His face warmed with benevolence as he raised his arms palm upwards in a gesture of peace. "Of course not," he roared.
Well, we shall see.Reuse content