The protagonist in Graham Greene's story is Trevor, or "T" as the boys in the gang call him. Yet, he is the protagonist in an ironic way since he is also the antagonistic force against the house. Another irony is that the anarchistic T, who wishes to destroy the only surviving house in the area that was bombed in World War II, is creative in his destruction, deciding that the house will crumble from within. 

Read on an allegorical level, T represents human nature that has been subjected to the effects of war and the resulting moral destruction of the soul. For, he is a boy devoid of any sympathies; he has no regard for property or even money. He believes in nothing:

T. stood with his back to the rubble like a boxer knoced groggy against the ropes. He had no words as his dreams shook and slid.

T's character is in great contrast to Mr. Thomas, "Old Misery," who talks of building things--"I'll have the wall built up...." When the boys trick him by saying that there is another in his "loo," he tells the boy beside him,

"I'm not unreasonable.  Been a boy myself. As long as things are done regular...Only it's got to be regular." 

When the boys go home that night, "The question of leadership no longer concerned the gang after their "long, tiring, unamusing job." For, they have exerted anarchy, having destroyed everything; they have even burned the money Mr. Thomas has stashed in his mattress. Born into destruction, these boys are nihilistic--without values or appreciation for anything. And, T, whose name having been reduced to a mere letter signifies nothing, represents this generation that lacks any values and can only live by continuing a destruction that eats at the very fiber of English existence.