Professor (highest academic rank) in the context of Tariq Ramadan

A Regius Professor is a university professor who has, or originally had, royal patronage or appointment. They are a unique feature of academia in the United Kingdom and Ireland. The first Regius Professorship was in the field of medicine, and founded by the Scottish King James IV at the University of Aberdeen in 1497. Regius chairs have since been instituted in various universities, in disciplines judged to be fundamental and for which there is a continuing and significant need. Each was established by an English, Scottish, or British monarch, and following proper advertisement and interview through the offices of the university and the national government, the current monarch still appoints the professor (except for those at Trinity College Dublin in Ireland, which left the United Kingdom in 1922). This royal imprimatur, and the relative rarity of these professorships, means a Regius chair is prestigious and highly sought after.

Regius Professors are traditionally addressed as "Regius" and not "Professor". The University of Glasgow currently has the highest number of extant Regius chairs, at fourteen.

Erasmus Smith's Professor of Modern History is a chair in history at Trinity College Dublin. It was founded in 1762 and funded by the Erasmus Smith Trust, which was established by Erasmus Smith, who lived 1611–1691. It had been preceded by a Professorship of Oratory and History in 1724, and in 1762 the original professorship continued as a Professorship of Oratory alone.

One of its incumbents was the celebrated J. B. Bury (1861-1927), author of History of the Roman Empire (1893), The Life of St. Patrick and his place in History (1905) and A History of Freedom of Thought (1914). The current occupant of the Erasmus Smith’s chair is Professor Jane Ohlmeyer, a historian of the seventeenth-century Irish nobility.

Sir Halford John Mackinder (15 February 1861 – 6 March 1947) was a British geographer, academic and politician, who is regarded as one of the founding fathers of both geopolitics and geostrategy. He is considered to have introduced the terms "manpower" and "heartland" into the English language. He was the first Principal of University Extension College, Reading (which became the University of Reading) from 1892 to 1903, and Director of the London School of Economics from 1903 to 1908. Initially a liberal and free market proponent, he shifted to support a protectionist and conservative view from 1903. While continuing his academic career part-time, he was also the Conservative and Unionist Member of Parliament for Glasgow Camlachie from 1910 to 1922. From 1923, he was Professor of Geography at the London School of Economics.