Childs was born in
Cornwall, the son of a solicitor. He initially entered the law himself, as an
articled clerk to his father. He was also a
captain in the 2nd Volunteer Battalion of the
Duke of Cornwall's Light Infantry (DCLI). When the
Second Boer War broke out he volunteered for overseas service, but was turned down. He decided to volunteer for regular service instead, intending to return to the law after the war, and in 1900 was commissioned into the regular DCLI, being immediately posted to the 1st Battalion in
Dum Dum, India. Shortly afterwards, the battalion moved to
Ceylon as a guard battalion for the Boer prisoner of war camp. After two years, the battalion was finally posted to South Africa, where Childs was appointed
adjutant and
quartermaster of the rest camp at
Stellenbosch. There he came to the attention of Colonel
Nevil Macready, then Chief Staff Officer at
Cape Colony, who appointed him garrison adjutant of Cape Town Castle. He was promoted lieutenant in April 1904 and returned to England in 1905, where he became adjutant of his battalion. He transferred to the
Royal Irish Regiment as a captain in 1910. In February 1911 Childs was seconded to the
War Office as a staff captain. In November 1910, he accompanied his old friend, Macready, by then Director of Personal Services, as his staff officer to
Tonypandy in
South Wales, where rioting had broken out. In February 1912, he was promoted to the brevet rank of major. In April 1914, he was appointed deputy assistant
adjutant-general at the War Office and, in September 1914, he was appointed assistant adjutant-general with the
British Expeditionary Force (BEF) and promoted to the temporary rank of
lieutenant-colonel and shortly afterwards to the temporary rank of
colonel. While with the BEF, he instituted
court martial reforms that increased the remission of death sentences for
deserters to 89 per cent of all those sentenced to death by military courts. In 1916, Childs returned to the War Office as assistant adjutant-general, mainly dealing with
conscientious objectors, and later the same year was appointed Director of Personal Services, in charge of Army discipline. In September 1915 he was given the substantive rank of major in the DCLI, in 1916 he became a brevet lieutenant-colonel, in 1917 a brevet colonel, and in 1919 a temporary
major-general. In 1919, he also became a deputy adjutant-general. ==Police career==