By the summer of 1979, Peter Sutcliffe had already killed ten women, but the investigation into his brutal crimes was about to take a fateful wrong turn, as police went public with letters and a tape sent by a man claiming to be the Yorkshire Ripper. Award-winning Daily Mail crime writer Stephen Wright speaks to retired Detective Chief Superintendent Chris Gregg, who joined the Ripper investigation as a young policeman, and who had serious doubts about the credibility of the so-called 'Wearside Jack' tape.

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