A junior partner to WT Jones in the firm of Jones and Middleton, Solicitors, on Glumangate, John Middleton specialised in advocacy, and in particular in agricultural cases. He was also keenly interested in country pursuits as a farmer and a member of the local hunt. From 1893 to his death in 1915 he served Chesterfield as Town Clerk (then a part-time post) as well as carrying out his legal duties. At the time of the Borough Extensions in 1892 he stood in for the ailing Town Clerk, John Cutts, and in recognition of his services was made a Freeman of the Borough in 1896.