Who is John McClure from By the Rivers of Babylon and what is their importance?

McClure is an American CIA agent, and passenger on El Al Concorde 02. His identity as a CIA agent is not known to most of those on board. To the other passengers he is simply an American Embassy man, going home on leave. A very tall man, he reminds others of Abraham Lincoln without a beard, and seems always to have a wooden match stick in his mouth. McClure seems never to get excited or emotional, taking things in stride. When the Concorde crash lands in Babylon, McClure takes a defensive position on the large hillside along the Euphrates River with Tom Richardson.