What is the theme in Last Orders by Graham Swift?

The bonds of friendship is the major theme in the book. The men in the story have been acquaintances for thirty years minimum. Some are good friends, while others merely tolerate each other. They live their lives and have their camaraderie at the pub, where most problems and tensions get smoothed over at some point. The main exception to this is between father and son, Jack and Vince. The other men have more of a bond to Jack, because he is their peer, while Vince is "the kid" in their eyes (even though he is over forty.) It becomes clear that Jack was the binding force of the group, because with him gone, tensions escalate.