At the end of 1912 Ross had resigned from his professorship at the Liverpool School of Tropical Medicine in order to practice in London. In November 1913 he was appointed Honorary Director of the Royal Society of Medicine’s Marcus Beck Laboratory where he was to continue his research on malaria, along with research on measles and dysentery, until 1917 when his appointment with the War Office became full-time.
The Marcus Beck Laboratory had been established by the Royal Society of Medicine to enable research to be conducted there by Fellows of the Society under the auspices of the Society. Ross was the first Honorary Director. Dr. David Thomson and Dr. John Gordon Thomson, both of whom had been working with Ross in Liverpool, also joined him in London and some of the financial support was provided by Sir Edwin Durning-Lawrence who had also financed some of Ross’s research in Liverpool. Both Edward Halford Ross and Hugh Campbell Ross, Sir Ronald’s two younger brothers, had previously moved from Liverpool to London, so that in many respects, apart from that of location, Ross suffered very little change in his working life.
After the outbreak of hostilities in 1914 Ross was appointed Consulting Physician in Tropical Diseases to the Hospitals for Indian Troops in England, which post he held in conjunction with his Royal Society of Medicine appointment until February 1917 when he became a full-time consultant at the War Office.