With a shortage of social housing, and the private rented market booming, reporter John Sweeney investigates the so-called 'rogue landlords' - the housing barons accused of receiving large amounts of housing benefit while using the small print in their tenancy agreements to exploit the poor and vulnerable. Councils say they don't have the right laws to combat them, but with the new housing minister ruling out any changes in the law, Panorama examines a problem that is not going to go away.