At the end of 1946 a man named Yitzhak Aharonovitch was sent to Baltimore to organise the refit of a dilapidated steamer, the President Warfield, which included a substantial upgrade of her engines. Under the Honduran flag – and with Aharonovitch at the wheel – the ship set sail for France the following spring. After taking on supplies in Marseille the ship sailed west to Sète, where she picked up 4,500 Jewish refugees who had managed to survive the Holocaust. In July 1947, the ship set out for Palestine, then still ruled by Britain. By then she had been given the resonant new name for which she would become famous – the Exodus.

The purpose of the Exodus’s voyage was to pile pressure on the British government to relax the limits it had imposed on Jewish immigration to Palestine since 1930. In early 1939, following an Arab revolt and with the prospect of another world war looming, the British had tightened the restrictions further. The Haganah, a clandestine militia formed to protect Jewish settlements in Palestine, had by then turned its energies to people smuggling in response to Nazi persecution: for a while the Nazis collaborated. While the Haganah was trying to save as many Jewish lives as possible, the Nazis hoped that by releasing Jews they could cause trouble for the British in Palestine.

A photograph from this era shows people wading ashore from a beached and listing ship into a beach full of sunbathers. Many of the refugees failed to evade the British, and there were two appalling catastrophes: in 1940 the Patria, a ship full of Jewish refugees the British were about to deport to Mauritius, sank in Haifa harbour with the loss of 263 lives after the Haganah used too much explosive in a bid to sabotage its engines. In early 1942 another ship, the Struma, sank in the Black Sea after it was denied permission to continue to Palestine. Of 769 aboard, only one survived. Eight weeks after the liberation of Belsen the Jewish Agency appealed to the British government to release more immigration permits: the end of the war, and a change of government, produced no change of policy.

Under international maritime law in peacetime the Royal Navy could only board ships in Palestine’s territorial waters which, at the time, stretched just three miles offshore, a distance that a ship like the Exodus could cross in less than ten minutes. As that left the British in the position of a goalkeeper, trying to save a penalty shot, they tried other means. In 1946 the government approved a plan proposed by MI6 to sabotage ships in port before they took on passengers and a create a whispering campaign ‘to make the flesh of prospective sailors creep’. Using intelligence gleaned from agents operating in the ports along the northern shores of the Mediterranean and radio intercepts, the Royal Navy rammed suspect vessels and towed them to Cyprus. In all some 50,000 Jews were incarcerated on the island.

In response, the Haganah bought the Exodus with funds raised through American supporters and prepared a trap. Although Aharonovitch, her captain, hoped that with the souped-up engines and intelligence he might be able to evade the Royal Navy’s coastal patrols, the Haganah did not want him to succeed. For that reason Exodus’s manifest included a disproportionate number of pregnant women, mothers with young children, the elderly and the sick. Her voyage was timed to coincide with the United Nations Special Commission which was then in Palestine, trying to decide its future.

The Exodus set sail tailed by a yacht carrying British saboteurs, but the British government recoiled at the risks entailed in disabling the ship and vetoed an attack. Instead it complained to the French government for allowing the ship to leave (the choice of Sète as a departure point was deliberate: its member of parliament was Jules Moch, the transport minister, who was Jewish, and his cousin was the top local official, the préfet). The foreign minister Georges Bidault – no friend of Britain, but that’s another story – disingenuously told the British ambassador that if the Royal Navy could intercept the ship, her passengers might be returned to France. In London the colonial secretary ordered the British high commissioner in Palestine to turn the Exodus’s passengers away, in order to ‘clearly establish the principle of refoulement’.

Refoulement entailed returning refugees to the country they had come from. As the colonial secretary’s phrase implied, in 1947, four years before the United Nations’ 1951 Convention relating to the Status of Refugees made it illegal, the practice was already controversial. Jewish refugees refused point blank to return home, not least because they knew antisemitism had not ended with the defeat of the Nazis. Regardless, two British destroyers rammed the Exodus when she was still in international waters and towed her into Haifa. There, her passengers were forcibly disembarked, while the members of the UN Commission looked on. They were rapidly shipped back to France, where, amid universal outrage in the press, the authorities did not try to make them disembark. The British then took the fateful decision to ship the refugees on to Hamburg, where it took a thousand British soldiers, and 1,500 German policemen, using water hoses, truncheons and tear gas to remove them from the ships, while brass band music was piped over a Tannoy in an attempt to drown out the screams of protest. Simultaneously, the UN Commission decided that British rule could not continue and that Palestine should be divided into separate Arab and Jewish states.

Amid calls on the British government to use the Navy to police the Channel and to revisit the 1951 Convention following its Supreme Court defeat, the Exodus affair should provide food for thought. The Royal Navy could not stop all the boats, even when it was far larger than it is today. And even, as in the case of the Exodus, when it did, public opinion made refoulement impracticable before the 1951 Convention rendered it illegal.