Along with Gertrude Bell and T. E. Lawrence, he was instrumental in creating and establishing the Kingdom of Iraq post-Ottoman rule, and he founded the nascent Iraqi government's laws and financial structure.

[4][6][7] Scion of an ancient, distinguished and aristocratic Jewish family of great affluence, the Shlomo-David's,[4][7] Sassoon was born on 17 March 1860 in Baghdad, Iraq.

[9][10] His father patriarch of the Eskell line of the Shlomo David dynasty Sassoon obtained his primary education at the Alliance Israélite Universelle[6] in Baghdad.

In 1877, at age 17, he travelled to Constantinople to continue his education, accompanied by his maternal uncle, the immensely wealthy magnate and land owner Menahem Saleh Daniel[11][12] who was elected deputy for Baghdad to the first Ottoman Parliament in 1876 during the reign of Sultan Abdul Hamid II and later became Senator of the Kingdom of Iraq (1925–1932).

Gertrude Margaret Lowthian Bell referred to him and his brother Shaoul in a letter to her father dated 14 June 1920, as follows: "I'm making great friends with two Jews, brothers—one rather famous, as a member of the Committee of Union and Progress and a deputy for Baghdad.

Sasun, with his reputation and his intelligence, ought to be a great help".Bell also wrote of Sassoon on 17 October 1920:"That night Mr Philby dined with me and we had a long and profitable talk.

To reach a final conclusion on the choice for ruler Winston Churchill, then British colonial secretary, summoned a small group of Orientalists to Egypt for the famous Cairo Conference[13] of March 1921.

Churchill's objectives were to save money by reducing Britain's overseas military presence; find a way to maintain political control over Britain's mandate areas as identified in the Sykes-Picot Agreement; protect what was then suspected to be substantial oil reserves in Iraq; and lastly preserve an open trade route to India, the Crown Jewel of the empire.

[14] Representing the Iraqis, two members of the council were picked to join the delegation: Sassoon Eskell and Jafar Pasha al-Askari; with the disliked Syed Talib left behind.

A little rigid, he takes the point of view of the constitutional lawyer and doesn't make quite enough allowance for the primitive conditions of the 'Iraq, but he is genuine and disinterested to the core.

that's a basis for carrying out the duties of a mandatory?” And again in correspondence dated 7 February 1921:"I do love Sasun Eff; I think he is out and away the best man we've got and I am proud and pleased that he should have made friends with me.

He has no wish to take any further part in public life but he says he is convinced that the future of his country—if it is to have a future—is bound up with the British mandate and as long as we say he can help us he is ready to put himself at our service.

He said that the stupendous efforts which had been exerted by the deceased in regulating and establishing on a solid footing, the affairs of the Kingdom of Iraq during the mandatory regime, will be remembered by future generations.

All leading Arabic daily newspapers similarly eulogised the late Sassoon's character and achievements, saying that the services which had been rendered by the deceased for the welfare of his country will immortalise his great name, adding that his death was an irreparable loss to the nation.