Who is Harold Saxon?

He gives the order to fire at the star in The Runaway Bride, he is an important name in The Lazarius Experiment, so I ume he is the Prime Minister, and maybe in charge of Torchwood. We saw the Dr being chased by the guards of Q.E. II, and know that Queen Vic banished him. So he is an enemy of the UK, so our nations P.M. would know all about him and want him out the way. Excellent series 3, not too sure about the human Darlek, can't believe that there is only one left. What does a Darlek eat? And is there a little hatch, like on a plane for the toilet. I don't think that this is the master, we saw him die in "The Movie", and found the Dr is part human, so many questions and sleepless nights.