Alan Blunt himself says Ethan Brooke is a very devious man, and likes things his own way. Ethan once was a colonel in the Australian Armed Forces, but a landmine sent him into hospital and then he became unable to work in military so he went into intelligence.
Ethan Brooke is famed for being a slanderer and bully: one Australian defence minister commented his clothes were casual because he wore jeans, and then Ethan did everything in his power to demote the man and make him work as a porter in a three-star hotel.
Ethan Brooke is also very cold and callous, he lies to Alex about saying he is passport control and then deliberately delays Alex and Jack's return to London, by saying he needs Alex for an assignment. Ethan Brooke also toys with Alex, and then makes Alex confused and stumble by bringing up Ash at the opportune moment. Ethan makes Jack feel bad by bringing up Ash and saying that Alex and Ash "would have a lot to talk about." Ethan is a very calculating man, even more so than Blunt, because whereas Blunt is reliable in that he does always send men to get Alex out, Brooke never cares about Alex, and leaves it to almost the last minute, when Alex is going mad with being lost in the Outback, that he sends men in and even then despite thwarting the Snakehead, Ethan isn't pleased to see Alex.
Ethan Brooke is revealed to have known Ash was a traitor and wanted to deliberately send him on the mission to get him killed and reveal his actions.