Born 2 August 1855 to Thomas and Mary Helen Lomax of Grove Park in Yoxford, Suffolk, Lomax joined the Scottish 90th Regiment of Foot as a junior officer aged eighteen in June 1874. In 1877 he went with the regiment to South Africa and participated in the 9th Cape Frontier War, and the latter phase of the Zulu War in 1878, seeing action at Kambula and Ulundi, which secured British victory in the campaign. Returning to Britain with his regiment Lomax was promoted to captain following the Cardwell Reforms which amalgamated his regiment into the Scottish Rifles in 1881.