Britain had promised the Jews a homeland in Palestine - but had also promised the Arabs freedom in all their lands in return for their support in the war against the Ottoman Turks. In reality, we broke our promise to both of them.
The Arabs watched Britain retreat from its obligations in the face of the UN's vote for an Israeli state; the Jews found that they got only half of Palestine - although Balfour had indicated that the whole of the territory might be their homeland. And when 700,000 Arab Palestinians fled their homes in what was to become Israel, we watched and - save for a few shots fired in defence of Haifa - forgot the victims.
Even today, the ruthless war fought out between Jew and Briton - and our failure to honour our promises to the Arabs - antagonise relations between Britain and Israel and between Britain and the Arabs. Neither side can forget what happened 50 years ago. Jews murdered Britons and Britons beat and hanged and sometimes murdered Jews. Arabs and Jews slaughtered each other for the land under Britain's control. When the last British troops packed their kit bags, they symbolised the end of empire and the end of any serious British role in Middle East politics for a generation. Many of them left under fire.
It all seemed simpler when Balfour made his declaration, anxious at the time to persuade world Jewry (especially in the United States) to support the Allied cause against Germany. "His Majesty's Government," he said, "view with favour the establishment in Palestine of a National Home for the Jewish People, and will use their best endeavours to facilitate the achievement of this object ..." Less attention was taken to Balfour's warning that "nothing shall be done which may prejudice the civil and religious rights of existing non-Jewish communities in Palestine."
Equally little attention has been paid since to the word "Palestine", for Britain was clearly envisaging all of Palestine - including what is now the West Bank (in antiquity, more Jewish than the Mediterranean coast) - as a Jewish "homeland". Jewish writers, with the brave exception of historians like Benny Morris, have paid equally little attention to Balfour's reference to "non-Jewish communities". And why should they? It was Balfour himself who wrote privately in 1918 that "in Palestine we do not propose even to go through the form of consulting the wishes of the present inhabitants of the country". For him, Zionism was "of far profounder import than the desire and prejudices [sic] of the 700,000 Arabs who now inhabit that ancient land".
And so it turned out. As Arab suspicion and then fury increased against the British, as they allowed European Jews into Palestine, so Jewish frustration increased at the British restrictions on immigration. Throughout the Second World War, Jew and Arab largely declared a ceasefire; many joined the British Army. Their graves lie together at Alamein - though when the then foreign secretary Malcolm Rifkind insisted that the Israelis should be allowed to commemorate their dead on the 50th anniversary in 1992, five Israelis flags - but not a single Palestinian flag - fluttered over the battlefield.
Moshe Dayan, future warrior of Israel, lost his eye to a Vichy French sniper liberating Lebanon in 1941.
Even before the war ended, the Palestine conflict resumed with bloodthirsty intent. In 1944, Jewish gunmen assassinated Britain's minister-resident in Cairo, Lord Moyne. The Observer blamed "Jewish fascism". In 1946, Menachem Begin's Jewish militants in Jerusalem blew up the King David Hotel, headquarters of British forces in Palestine - a "terrorist" act if ever there was one, the ninth-most horrific this century, according to the British. It killed 91, including Arabs and Jews. The Jewish Agency denounced the bombing - though few Jews could forget how Britain persuaded the Turks to prevent east European Jews travelling through the Bosphorous to Palestine in their flight from the Nazis. Those Britons who had fought and died to liberate the death camps of Europe were now being attacked by the survivors in Palestine. The British hanged Jews for "terrorism". The historian Martin Gilbert, in his new history of Israel, recalls the names of three: Avshalom Haviv, Yaakov Weiss and Meir Nakar.
In revenge, the Jews hanged two British Army sergeants - whose names, Marvin Paice and Clifford Martin, are not recorded by Mr Gilbert in his new book. Their bodies were booby-trapped after their strangulation.
"Must our Boys Die?" the Daily Mail asked, urging an early British retreat. The Mail got its way. The Times commented with prescience that the violence in Palestine was "a fan to flame the smouldering resentment of the Arabs who campaign already that they are victimised by terrorism and now threaten in their turn to resort to force". The British left behind them a resentful Israel and a cruelly dispossessed community of Palestinians, most of whom held deeds to their land issued by the British mandate authorities as well as the Ottomans. Their brown Palestine passports were identical to those of the British, complete with lion and unicorn and "Dieu et Mon Droit" at the top. But they had no rights. The British, for all their First World War promises of independence for the Arabs, no more protected the Arabs of their mandate than the Jews.