Gertrude Bell, a commander of the Order of the British Empire and also an archaeologist, contemporary and colleague of T.E. Lawrence (of Arabia), was principally responsible for producing the analysis upon which the boundaries of the modern Middle East were drawn.
Lawrence, Emir Faisal, and others at Versailles - 1919
After the Sykes-Picot agreement was put into effect during the Treaty of Versailles proceedings, where responsibility for the War was meted out to those who had initiated the Armistice, Bell and Lawrence attended the Cairo Conference of 1921 which created the states of Jordan and Iraq and utilized Bell's work.
The British Empire was bankrupt, as part of a long economic decline that really began in the eighteenth century due to the unsustainable nature of mercantilism but would not become detectable until after the First World War had ended and someone had to pay the bills, finally. Indeed, post WWI Britain grew to its greatest extent as the colonial territories of Germany were annexed as well as the former provinces of the Ottoman Empire.
The Depression and the rising sun of Imperial Japan, which made Britain look like the "sick man" of Asia with an incredible string of lopsided victories over England and its colonial forces both prior to, and immediately after Pearl Harbor exposed the decay and decline of the empire. Indeed, the war in the Pacific was fought by those who had mostly kept out of WWI, which was the first act in a two act play - separated by a 20 year intermission. After reloading, WWII commenced, and some of the open issues after WWI were settled, while others remain unsolved to this day. Care to hazard a guess what they are?