Destroying Mr. Thomas' grand old house is all Trevor's idea. After all, he is the first one to 'scope out' the place as a potential target. T presents the idea to the gang as an amazing opportunity to do something that no gang has done before:
‘They’d never know. We’d do it from inside. I’ve found a way in. We’d be like worms, don’t you see, in an apple. When we came out again there’d be nothing there – nothing but just walls, and then we’d make the walls fall down – somehow.’
The gang is motivated by their desire to prove themselves worthy to the task of pulling the house down. The challenge of the physical task appeals to their creative, destructive talents immensely.
The Wormsley common gang also wishes for fame and increased notoriety. Blackie predicts that "the fame of the Wormsley Common car park gang would surely reach around London." It is important to note that the boys are extremely resistant to doing anything that they perceive might land them in "the jug" like "pinching things;" the boys naively do not see their act of destroying the house as a criminal activity.