What Happened to the Jack the Ripper Letters?

Sunderland police played the tape and letters all over the north of England. A team of 15 officers with handwriting analysis training checked more than 100,000 applications for local council houses and 7,500 letters from men on probation. They would end up checking a total of around 15 million letters. Detective Zacharisson realised something that Oldfield and Dick Holland and everybody else on their team had missed. The first letter sent in early March 78 teased Oldfield saying he was wrong about there being seven ripper murders. But what had been missed by everyone up to this point was that if you included Joan Harrison's murder, then they were actually nine.