Crompton, Rookes Evelyn Bell (1845-1940), engineer, was born at Sion Hill, near Thirsk, 31 May 1845, the fourth son and youngest child of Joshua Samuel Crompton, by his first wife, Mary, daughter of Sir Claud Alexander and a friend and pupil of Mendelssohn. The names Rookes Evelyn record his kinship through the Rookes, his grandmother's family, with the diarist John Evelyn.
During the Crimean war Crompton was allowed to accompany Captain (Sir) William Houston Stewart, his mother's cousin, commander of the Dragon; and was officially enrolled as a naval cadet. He visited his elder brother in the trenches and actually came under fire; thus at the age of eleven he had the Crimean medal and Sebastopol clasp.
School at Elstree prepared Crompton for Harrow (1858-1860). During his holidays he built, in a workshop at home, a full-size steam-driven road engine; but before his true engineering career began he served for four years in India (1864-1868) as an ensign in the Rifle Brigade. Even there, however, he equipped a travelling workshop and had his machine tools sent out from England. His strong views on the inefficiency and slowness of the bullock trains impressed R. S. Bourke, Earl of Mayo, then viceroy, and within a short time Crompton introduced steam road-haulage, receiving a government grant of £500 for his services.
Returning in 1875, Crompton left the army and bought a partnership in a Chelmsford engineering firm, and, when adviser at the Stanton iron-works belonging to the Derbyshire branch of his family, purchased some of the new Gramme dynamos in order to improve the lighting of the foundry. Their success provided a turning-point; from that date (1878) electricity and engineering became for him almost inseparable. Co-operating with Emil Burgin, of Basle, who was then working on dynamo design, Crompton obtained the rights of manufacture and sale of Burgin's machine, improved it, and developed it to commercial success. He began making electric light plant, and carried out many installations, those at the Mansion House and the Law Courts in London and the Ring Theatre in Vienna being especially notable. In 1881 the firm of Crompton's was awarded the first gold medal ever given for electric lighting plant.
Towards the end of 1886 Crompton formed the Kensington Court Company, financed by a few friends, for electricity supply to neighbouring premises. This pioneer enterprise, one of the first of its kind, became the Kensington and Knightsbridge Electric Supply Company. Crompton advocated the direct current system; S. Z. de Ferranti, engineer of the London Electric Supply Corporation, believed in alternating current and led the opposing school. The resulting ‘battle of the systems’, with these two as friendly antagonists, has its place in electrical history.
Between 1890 and 1899 Crompton revisited India, advising the government on electrical projects. On his return he took charge of a volunteer corps of Electrical Engineers, and by May 1900 was in South Africa with his men, whose efficiency in maintaining communications and skill in emergencies won high praise. Crompton had gone out as captain: on his return, later that year, he was promoted lieutenant-colonel, appointed C.B., and retained as consultant to the War Office on the development of mechanical transport.
Although electrical matters still claimed much of his time, Crompton became increasingly occupied with road transport. He had been a founder-member of the Royal Automobile Club in 1896, and was one of the judges in 1903 at the first motor show; as engineer-member of the Road Board appointed by the government in 1910, he improved road construction practice and materials. In the early part of the war of 1914-1918 Mr. Churchill consulted Crompton upon the design of an armoured vehicle capable of crossing trenches, and he was responsible for producing a type of landship, which later evolved, under various hands, into the tank.
In his laboratory at 'Thriplands', his Kensington home, Crompton spent many hours at research. He served on the committee of the National Physical Laboratory, and his advocacy of a closer understanding between all countries on electrical affairs resulted in the founding of the International Electrotechnical Commission in 1906, of which he was the first secretary.
In 1927 the firm of Crompton's became merged with another under the title of Crompton, Parkinson, & Company, Limited. 'The Colonel' was then over eighty, but still active, and he retained a directorship in the new concern. A dinner in his honour, held in London in 1931, was attended by probably the largest gathering of distinguished scientists and engineers ever recorded at a personal function. Each of the three principal engineering bodies, the Civil, Mechanical, and Electrical, made him an honorary member; he was twice president of the Institution of Electrical Engineers, in 1895 and again in 1908. He was awarded the Faraday medal in 1926 and was elected FRS in 1933. His ninetieth year was celebrated by another banquet, at which Sir James Swinburne presented him with his portrait by George Harcourt, which is now in the possession of the Institution of Electrical Engineers.
Professionally, Crompton was the expert, commanding respect and admiration; socially, a host of friends regarded him with affection. Young men benefited by his cheerful attitude to life, his resource and originality, and often by his generous help.
Crompton married in 1871 Elizabeth Gertrude (died 1939), daughter of George Clarke, of Tanfield, near Ripon, his father's other estate in Yorkshire; they had two sons, one of whom predeceased his father, and three daughters. His wife was his constant companion, keenly interested in all his enterprises. He died at Azerley Chase, Ripon, 15 February 1940.