Baring all makes for quite a striking portrait

John Singer Sargent's portrait of Evelyn Baring, 1st Earl of Cromer, painted in 1902, which illustrates the front cover of Roger Owen's masterful biography of Cromer, almost says it all. It shows the Consul-General of Egypt at the height of his powers seated at his desk in a corner of his Wimpole Street study in front of a line of leather-bound state papers. His hair and moustache are white and his eyes seem a little tired and unfocused, but there is no doubting the authority and power of a figure who was among the greatest of all British imperial administrators - "the greatest ruler that Egypt has had since the days of the Pharaohs", in the words of a Spectator review of the portrait.

Only Cromer's adversary Wilfrid Blunt, the poet and anti-imperialist diplomat, seriously disagreed, remarking that the painting portrayed Cromer as having "bloated cheeks, dull eyes, ruby nose and gouty hand, half torpid, having lunched heavily".

During the heyday of the British Empire before the First World War, Cromer ruled Egypt for nearly a quarter of a century, from 1883 to 1907, and was perhaps second only to Lord Curzon in prominence and public renown. Like Curzon and many of his contemporaries, Cromer regarded imperial possessions as central to Britain's global standing and their misgovernment as a step in the direction of "national decay and senility".

Owen makes full use of his subject's official correspondence in the Foreign Office, as well as the Cromer family papers. The most important source is, however, a 400-page volume of Cromer's "biographical notes" bound and dated November 1905. These provide much of what is known of Baring's private life until he went to India in 1872 at the age of 31, and describe the transition from "indifferent schoolboy... to a hedonistic spendthrift young army officer, and then to personal reformation as a result of a good woman and the example of fellow officers and friends much better educated than he".

Indeed, these notes were the main source for the first, official, biography of Cromer, published by the Marquess of Zetland in 1932, a decade and half after Cromer's death in 1917. With some difficulty, I managed to track down and read this earlier book, which gives an eerie impression of having been "inspired from the grave". It seems virtually to be a ghost-written autobiography. Owen, of course, does not fall into the same trap. Although he relies on similar sources to Zetland, he does not suppress, for example, the facts surrounding Cromer's illegitimate daughter by his mistress in Corfu and his near-disastrous row with Lord Ripon, the Viceroy of India, in 1881.

Baring, born in 1841, was the grandson of Francis Baring, who founded the family's merchant bank in 1762. His childhood in Norfolk, his military education, his career as a staff officer and his garrison life in Corfu and Malta are covered in detail by Owen.

Then, after a year's apprenticeship in imperial government and international finance, Baring became private secretary to his cousin Lord Northbrook, who had been appointed Viceroy of India in 1872. He married Ethel Errington four years later and she became an enormously supportive influence.

His first contact with Egypt came in 1877, when he was asked to help sort out the Khedive's finances. Then, in 1880, he returned to India as the financial member of the viceroy's council. Despite the friction with Lord Ripon, he eventually became his right-hand man, which is what led to his appointment in 1883 as Consul-General in Egypt with the special rank of Minister Plenipotentiary in the diplomatic service.

As soon as he arrived in Cairo, Baring - who became Baron Cromer in 1892 - realised that the British had to be given more control if the country was to be governed properly. Indeed, the biography of Baring after 1883 is almost the history of Egypt in this period.

The administration of the country then was almost hypothetical, and the finances were in complete disarray. Baring immersed himself in overhauling the tax and revenue systems. He also abandoned temporarily Egypt's authority over the Sudan, which led to General Gordon's ill-fated mission to Khartoum. In due course, new departments of government were formed or reorganised to a point where Egypt's administration was said to be the most efficient of any British colony or protectorate.

Then, in 1897 and 1898, Cromer moved to recover Egypt's position in the Sudan under the military leadership of Kitchener, thus securing the financial interests of both Egypt and Great Britain against the hostile ambitions of the Italians, Belgians and French. Egypt had come of age and Cromer found himself ruling as its potentate until 1907, when he resigned through ill-health. In 1909, his two-volume Modern Egypt brought him considerable literary success.

Cromer had some severe political critics. Most Egyptians, then and now, abhor him for sacrificing the country's educational progress at the altar of British commercial success - and this argument damaged Cromer's reputation after the First World War. Nevertheless, he remains a key figure in the evolution of modern Egypt up to the time of Nasser's 1952 coup.

Perhaps Lytton Strachey's famous passage in Eminent Victorians , quoted by Owen, is still the best comment on Cromer: "When he spoke, he felt no temptation to express everything that was in his mind. In all he did he was cautious, measured, unimpeachably correct... His temperament, all in monochrome, touched in with cold blues and indecisive greys, was eminently unromantic. He had a steely strength.

"Endowed beyond most men with the capacity for foresight, he was endowed as very few men have ever been with that staying power which makes the fruit of foresight attainable. His views were long, and his patience even longer.

He progressed imperceptibly; he constantly withdrew; the art of giving way he had practised with the refinement of a virtuoso. But, though the steel recoiled and recoiled, in the end it would spring forward."

Lord Cromer is an authoritative examination of an extraordinary British statesman. It is also an intelligent assessment of the often-bitter legacy of imperial rule.

Christopher Ondaatje is a council member of the Royal Geographical Society and the author of Hemingway in Africa .