Mr. Diagoras (portrayed by Eric Loren) was a ruthless businessman who appeared in the Doctor Who episode "Daleks in Manhattan". During the Great Depression of 1930, he oversaw the construction of the Empire State Building in New York. Cold and uncaring, he hired homeless people and worked them to the bone for less than minimal pay.
When the Cult of Skaro escaped from the Battle of Canary Wharf in 2007, they emerged in 1930's New York and persuaded Diagoras into assisting their plans, essentially taking over the Empire State Building project. Diagoras was provided with Dalekanium alloy plates to use in constructing the mast at the top of the tower and was also instructed to recruit more personnel that the Daleks could use for their Final Experiment.
Mr. Diagoras was "rewarded" for his service to the Cult of Skaro when he was introduced to their leader, Dalek Sec. The corrupt entrepeneur was restrained within the Daleks' laboratory beneath the ESB and Dalek Sec decided to use him for the Final Experiment. After injecting himself with a new hybridisation solution, Sec opened his robotic shell and pulled Diagoras inside with him, beginning a process of merging. When Sec's shell later re-opened, Diagoras and the Dalek had bonded into a single body. Sec's consciousness remained dominant, though he gained certain human psychological qualities from Diagoras. Apart from that, Diagoras essentially ceased to exist following the merger.