A new kind of guerrilla action is emerging. Like the soldiers of the same name， its proponents are pitted against authority， using ambush and surprise as their primary weapons. Their interests， however， are far from violent: gardening， music， and film-making， to be exact. Guerrilla is now used to refer to activities performed in an impromptu way， often without permission. Guerrilla gardening involves activists planting seeds on abandoned or public land， usually in secret. Then there are the independent film-makers on low budgets， who shoot their scenes quickly in real locations. Or how about guerrilla rockers, who perform unexpectedly in unlikely places: their live shows have become legendary， including guerrilla gigs on a tube train and in the BBC's foyer.