Douglas Duff arrived in Palestine as a Black and Tan and rose to Police Inspector for Jerusalem. He recorded, in his own later writing, an Arab brothel-keeper asking him, trembling, whether he belonged to the new police force sent to Palestine because of the murders committed in the land the English had been driven from on account of their brutality. The propaganda had beaten the force to the docks. Palestinian Arabs knew who was disembarking at Haifa before the ships had finished tying up.
The reputation was earned in real time and not by rumor alone. Duff carried an Irish blackthorn baton, a Colt .45, and a Turkish whip, and later admitted, in his own words, to going berserk while charging unarmed crowds. He introduced waterboarding and suspension torture into Palestine's prisons; other colonial police coined the phrase "duffing up" as slang for torture, in direct reference to him. He was eventually convicted and dismissed from the force for counseling and procuring a subordinate to inflict bodily distress on a Palestinian prisoner — a conviction that did not end his career in Palestine so much as pause it.
By the time of the Arab Revolt, from 1936 to 1939, the Palestine Police had swelled from around 700 to over 2,800, and the tactics that had defined the Black and Tans in Ireland came back in full: home demolitions, warrantless arrests, collective punishment of entire villages, beatings, torture. The Times of London and the New York Times covered it as British order-keeping against Arab rebels — the exact inverse of how the same conduct had been covered when it happened in Ireland fifteen years earlier. The High Commissioner himself sent a secret telegram to London in September 1938 flagging the emergence of what he called Black and Tan tendencies inside his own police force. Nobody acted on it.
The Jewish community's relationship with that same force ran a different course before it converged with the Arab one. In the short term, some Zionist settlers saw the Gendarmerie as protection — Palestine Police had broken up the 1920 and 1921 Arab riots in incidents where Arab constables had themselves joined the attackers, and the British force, in that narrow window, looked comparatively protective of Jewish communities. That did not survive contact with Duff.
On September 23, 1928, Duff and four of his former Black and Tan colleagues forcibly removed a screen Jewish worshippers had erected at the Western Wall for Yom Kippur prayer, and in the struggle a man clinging to the screen was thrown into the valley below. Zionist leaders publicly denounced the Palestine Police afterward and drew the Black-and-Tan comparison explicitly and by name; three separate assassination attempts targeted Duff in the weeks that followed. The screen incident and what came next are not the same event, and the distinction matters: nearly eleven months later, in the last week of August 1929, a much larger wave of communal violence broke out across Palestine — 133 Jews and 116 Arabs killed — a downstream consequence of the tension Duff's conduct had helped set alight the previous September, not a continuation of the same afternoon.
Jewish members of the Palestine Police later claimed they had learned interrogation technique from Duff directly — specifically, how to torture without leaving a mark. The claim may have grown in the retelling. What can be stood on is narrower: Duff brought the methods, other officers in the same force used them, and a number of those officers were still in Palestine when the Mandate ended. What any of them carried into the services that outlasted the Mandate is a separate question.