Prime Minister Boris Johnson toured HMP Leeds, where staff told him the introduction of a state-of-the-art scanner had led to a reduction in drug smuggling and therefore violence.
Mr Johnson spent around 90 minutes touring the prison in the Armley area, where he talked to managers, guards and inmates.
He was given a demonstration of an £80,000 torso and body scanner which is used on new inmates, recalled prisoners and those who have been to court, and which uses sophisticated X-ray imaging to detect contraband.