William Sofield, of Studio Sofield, is designing all the interiors at the Flatiron. The studio’s clients include Tom Ford, Madonna and Mary-Kate Olsen, as well as the Soho Grand Hotel and Core private members’ club, but this is in a different league. He is clearly deeply in love with the building. Showing me bits and pieces from the original architecture in his Bleecker Street penthouse studio (which, perfectly, is in the only New York building designed by the greatest Chicago architect of them all, Louis Sullivan), Sofield pores over old photos, drawings and pieces of hardware.