Brackenbury Bayly was educated at Wellington College, England, and was appointed in the Engineering Branch of the British postal telegraph service in January 1872. In February 1877 he came to the Cape Colony and started work as an inspector in the Cape colonial telegraph service. During the Anglo-Zulu War of 1878-1879 he was seconded to Natal and the Transvaal for telegraph construction, receiving the Zulu War Medal with clasp in 1879. He was responsible for the construction of several important telegraph lines in the Cape Colony, Natal, and the Transvaal. He married Beatrice M. Coope in 1888 and they had two children.
In August 1886 Bayly was appointed district engineer for the telegraph service in the western districts (with headquarters in Cape Town), and in the same post for the metropolitan district in September 1896. He became Chief Technical Officer of the Post Office in Cape Town in July 1902. His hobbies included sport and scientific pursuits.
In May 1904 Bayly read a paper on "Radium" (discovered in 1898 by Madame Curie) to the Cape Society of Civil Engineers. It was published in the society's Minutes of Proceedings (Vol. 2), although he was not a member. He was, however, elected an associate of the (British) Institution of Electrical Engineers in 1877, became a member in 1886, served on the committee of the Cape Town local centre of the institution in 1900, and was its chairman during 1902-1903.