They used the actual road for the exteriors – buy it on DVD and judge for yourself. I recall visiting the realistic Whitechapel streets interior sets and interviewing veteran star James Mason, who was playing Dr Watson. The Metropolitan Police twice invited me to visit the world-famous Black Museum at Scotland Yard, although I think they now call it the Crime Museum due to complaints. He was executed over there and Scotland Yard asked for his fingerprints so they could close their case file. The ever-efficient Germans cut off his hand and sent it so Scotland Yard so they could take their own prints.