Innocent woman shot in the chest. Student dragged into an alley by two men. And assassins sticking shotguns through the letterbox... GUY ADAMS reveals how Cardiff has become overrun with gangs and addicts - and crack cocaine war behind it

On a warm June evening, two young men approach the front door of a red-brick house in Cardiff. But they are dressed entirely in black, wearing balaclavas. And one brandishes a shotgun.