John M. Liddell was a certified manager of British coal mines and an associate member of the North of England Institute of Mining and Mechanical Engineers. In 1886 he and J.H. Merivale contributed a paper on "Transmission of power by steam" to the institute's Transactions, published in Newcastle-upon-Tyne.
By 1883 Liddell was in Cape Town, from where he applied for employment in Natal as a mining engineer or surveyor. By August 1886 he was practising his profession in Barberton, a town that had been proclaimed two years earlier after gold was discovered there. He advertised in the local press as a mining engineer and surveyor, formerly of Newcastle-upon-Tyne and Kimberley. He was a member of the short-lived Barberton Association of Civil Engineers (1887-1888), which petitioned the government of the South African Republic (Transvaal) without success to officially recognise the profession. In June 1888 he became a foundation member of the second scientific society to be established in the town, the Barberton Scientific and Literary Society (1888-1889). He served on the committee which drew up the society's rules and which elected a president and vice-president. At the third monthly meeting in August that year he delivered an address on "The progress of mining", discussing aspects such as exploration, shaft sinking, ventilation, drainage, ore transport, and mining laws, though with reference mainly to coal mines in England. The paper was published in the society's Proceedings, which were issued separately after each meeting.
In 1891 Liddell contributed a paper on "The goldfields of the valley of De Kaap, Transvaal, South Africa" to the Transactions of the North of England Institute of Mining and Mechanical Engineers (Vol. 38, pp. 171-175). He moved to the Witwatersrand around this time, for in 1893 he published a paper on "The Witwatersrand gold-fields" in the same journal (Vol. 41, pp. 155-159). In January 1894 he applied for a post as mining inspector in the South African Republic (Transvaal).
In 1902 J. Liddell, probably the same person, became a foundation member of the South African Association for the Advancement of Science. By 1903 he was Chief Mechanical Engineer of De Beers Consolidated Mines, Ltd., Kimberley.