[4] He then began studying for a doctorate from the Royal Free Hospital School of Medicine in London.

In 1963, he briefly moved to the United States for his education, settling in Ann Arbor, Michigan but travelling throughout the country, engaging with politics and becoming more involved with Christian evangelism, participating in missions led by Billy Graham.

[4] He obtained his PhD in 1969, with thesis title Studies on the effects of radiation on mammalian bone grown in vitro.

[5] He worked as assistant professor of radiation research at the University of Iowa from 1968 to 1970 and then returned to the Royal Free Hospital School of Medicine as a lecturer from 1970 to 1984.

[7] He also campaigned prolifically against pornography: he introduced a private member's bill in 1979 to ban indecent images and posters outside cinemas, sex shops and strip clubs, and in early 1980, he called for Keith Joseph to launch an inquiry into a page on the Post Office's Prestel viewdata service, called "A Buyer's Guide to Dirty Books".

[15] Lord Mawhinney questioned the priority David Cameron had given to the Marriage (Same Sex Couples) Act 2013, stating that it was a distraction.

In 1964, Mawhinney married Betty Oja, an American citizen whom he met during his time in Michigan; the couple had three children.