Two leading Russian bankers targeted by EU sanctions have resigned as directors of their European-based overseas investment firm, which is advised by Denis O’Brien. LetterOne, also known as L1, confirmed to The Currency this Tuesday that Mikhail Fridman and Petr Aven had resigned from their board seats after their inclusion on the EU sanctions list on Monday. L1 was founded in 2013 by Fridman and Aven along with German Khan, Alexey Kuzmichev and Andrei Kosogov. All are also partners in Alfa Group, which includes Alfa Bank, the largest private bank in Russia. Irish businessman Denis O’Brien is a member of…