“In 1864 he was in the General Manager’s office at Derby, pleasingly varying his clerical duties by drawing caricatures for the amusement of his fellow clerks, and designing cartoons for the local satirical journal, the “Derby Ram,” which appeared spasmodically and devoted itself principally to electioneering purposes. One of his colleagues was Henry Lemon, Mark’s son, who showed his father some of his friend’s sketches. On the occasion of a subsequent visit paid by Mr. Atkinson to town, Mark Lemon invited him to dine at the Garrick Club (whither they drove in a hansom, much in the style shown in the sketch), and Shirley Brooks drank to him as “the future cartoonist of Punch.” His first cut -- an initial T -- appeared on page 15, Vol. XLVIII.”
Quote from The History of Punch, by M. H. (Marion Harry) Spielman, London: Cassell, 1895. Spielman (1858-1948) was the editor of The Magazine of Art (1878-1904) where he published numerous articles on caricature by himself and others.