 While studying at Oxford's Lincoln College, Marston worked under Nobel Prize-winner Howard Florey, Norman Heatley and other scientists from the research team that developed penicillin as the first antibiotic, and graduated with a degree in research science.After completing his internship at Johns Hopkins Hospital in Baltimore, Maryland, and a one-year residency at Vanderbilt University Hospital in Nashville, Tennessee, Marston joined the National Institutes of Health (NIH) as a medical researcher with the Armed Forces Special Weapons Project, examining the infectious after-effects of whole-body irradiation, from 1951 to 1953.He finished his residency at MCV in 1954.