Who is the popular contemporary author who is on an on-going mission to 'prove' that English painter Walter Sickert is the actual Jack the Ripper?

Patricia Cornwell has been involved in a continuing, self-financed search for evidence to support her theory that painter Walter Sickert was Jack the Ripper. She wrote Portrait of a Killer: Jack the Ripper—Case Closed, which was published in 2002 to much controversy, especially within the British art world and among Ripperologists. Cornwell denied being obsessed with Jack the Ripper in full-page ads in two British newspapers and has said the case was "far from closed". In 2001, Cornwell was criticized for allegedly destroying one of Sickert's paintings in pursuit of the Ripper's identity. She believed the well-known painter to be responsible for the string of murders and had purchased over thirty of his paintings and argued that they closely resembled the Ripper crime scenes. Cornwell also claimed a breakthrough: a letter written by someone purporting to be the killer, had the same watermark as some of Sickert's writing paper. Ripper experts noted, however, that there were hundreds of letters from different authors falsely claiming to be the killer, and the watermark in question was on a brand of stationery that was widely available.