Rothermere became the Chairman of Associated Newspapers in 1970, taking over from his father Esmond Cecil Harmsworth, 2nd Viscount Rothermere, who had Alzheimer's disease. He was responsible for the relaunch of the "Daily Mail" as a tabloid, after which its circulation increased greatly under editor Sir David English. He may also be considered the founder of "The Mail on Sunday". After the death of his father in 1978, he also became chairman of parent company Daily Mail and General Trust plc (DMGT). He attempted to combine the companies in a manner calculated to avoid taxation. An artefact of this plan was the ownership of Associated Newspapers being vested in Associated Newspapers Holdings (ANH), ownership of which was split 50.2%-49.8% between DMGT and its wholly owned subsidiary Daily Mail & General Holdings (DMGH). (Since that time DMGH's name has been transferred to ANH, and the old DMGH has become Derry Street Properties)..