Mansel's first book, Louis XVIII, was published in 1981 and this - together with subsequent works such as Paris Between Empires 1814-1852 (2001) - established him on both sides of the Channel as an authority on the later French monarchy. Six of his books have been translated into French.

Altogether Mansel has published nine books of history and biography, mainly relating either to France or to his other main area of interest, the Ottoman Empire and the Middle East: Sultans in Splendour was published in 1988 and Constantinople: City of the World's Desire 1453-1924 in 1995.

In 1995, Mansel was a co-founder of the Society for Court Studies, together with David Starkey, Robert Oresko and Simon Thurley, and he is the editor of the Society's journal, The Court Historian. He is a Fellow of the Royal Historical Society, the Institute of Historical Research (University of London), and the Royal Asiatic Society, and a member of the Conseil Scientifique of the Centre de Recherche du Château de Versailles.