[8] McKerron joined the Malayan Civil Service in 1920[9] was appointed as acting assistant superintendent in the Monopolies Department (Singapore).

[15] In 1932, he was the secretary of Federated Malay States Retrenchment Committee and in the following year, he appointed Superintendent of Taiping Convict Establishment.

The objective of the registration is avoid the tragic mistakes of the First World War when thousands of men enlisted and went to the front who would have been of far greater value to the country in their civil posts.

[26] During the period of British Military Administration in Malaya in 1945–1946, Brigadier McKerron was the Deputy Chief Civil Affairs Officer in Singapore,[27][28] assisting Major-General Sir Ralph Hone (Chief Civil Affair Officer of Malaya).

After the British Military Administration ended on 31 March 1946, McKerron was sworn in as the 1st Colonial Secretary of Singapore on the following day.

[28] During his tenure as colonial secretary, McKerron was sworn in as Officer Administrating the Government when Sir Franklin Gimson (Governor of Singapore) was away in England for a period of 5 months in 1947.

[2][35] McKerron was invested with Companion of the Most Distinguished Order of St. Michael and St. George (CMG) in 1945 in recognition of his work in the Malayan Planning Unit during the war in Malaya.