[10][11][7] Dallen was named a Foreign and Commonwealth Office Scholar to the University of Oxford where he received a M.A.
[2][7][4] His master's thesis at Oxford, "An Overview of European Community Protection of Human Rights, with some Special References to the U.K.", was named Article of the Year by the Common Market Law Review and published in book and journal form by them in 1990.
[16][17] Dallen served on the editorial board of the Southern literary magazine Oxford American and The Hemispheric Review.
[7] When The Daily Journal ceased publication in 2008, its successor was the online newspaper, the Latin American Herald Tribune.
[5] Dallen was a frequent commentator in print, and on radio and television about South American affairs.
[3] Dallen's investing was chronicled by the Financial Times in a 2014 article, saying, "…The basket of defaulted Argentina bonds, bought by Dallen for clients last year when they were trading for 30 something cents on the dollar, rose through the mid 1980s to reach a bid price of 90 cents on the dollar."
[56][57] In early 2016, Dallen began warning that Venezuela would default on its billions in foreign debt, telling Reuters that "It is a question of when, not if," and noting that "The only thing that could change that is a sharp recovery in oil prices, and/or a bailout from Venezuela's friends in China, Russia or Iran.
[63][64][65] The Financial Times in an article titled "Venezuela stopped bond payments in September" credited Dallen with the discovery and proof.
[67][68] Dallen was a member of the International Law section of the New York State Bar Association.