Christopher Wren was also the architect of the house that the boys destroy, St. Paul's was his masterpiece.
The boys have gotten so used to destruction from the war all around them, that they themselves become destructors. Christopher Wren represents builders, the opposite of destruction.
Christopher Wren was an architect who built St. Pauls' Cathedral in London. This is a very vital piece of information because we know that St. Paul was one of the few who escaped the bombing of houses in England by Hitler. This ultimately refers to the fact that Greene is portraying war through the two main elements in this story namely the members of Wormsley Gang and the house. The house represents St. Pauls Cathedral and the historical perspective it had.