Neilson’s hardened criminal behaviour became more entrenched with each robbery and, on 15 February 1974, during a raid on a Harrogate sub-post office, he shot dead the postmaster, Donald Skepper. Having kept a low profile following the first murder, and the ensuing police hunt, he took another life seven months later, when postmaster Derek Astin was shot dead in Lancashire during the course of another raid. The police quickly came to the conclusion that they were looking for the same killer in both cases.
Just 9 weeks later, a third postmaster, Sidney Grayland, was shot dead during the commission of a robbery in the West Midlands. Forensic evidence at the scene linked this death to the first two. Despite the three deaths the media showed little interest in the attacks, and Neilson was dissatisfied with the lack of attention, as well as the relatively slim pickings to be had from the post office raids.
Still searching for that elusive big payout, Neilson settled on kidnapping as his best route to success, choosing Lesley Whittle, a 17-year-old heiress to a transport fortune. He gathered as much information about her as he could, and made comprehensive plans for her incarceration, as well as the delivery of the ransom that he planned to demand for her return.
On 14 January 1975, Neilson broke into the Whittle family’s Shropshire estate, and abducted Lesley from her bedroom without incident, leaving a ransom note that demanded £50,000. In it, he gave detailed instructions for its delivery by Lesley’s brother, Ronald, and included a warning not to involve the police. Lesley Whittle was held in a drainage shaft beneath Bathpool Park, in Staffordshire.
The Whittle family chose not to heed the ransom warning, and informed both the local police and Scotland Yard of the abduction. Poor communication between the different police factions led to a media leak, which convinced police that the kidnapper had been scared off by the media attention. This wasn’t the case, however, and when Neilson called the designated phone box in accordance with his ransom instructions, Ronald Whittle was not there to take his call.
Two further ransom delivery attempts were bungled over the next 72 hours, as a result of both poor police coordination and bad luck, but at least police were sure that Lesley was still alive at this time, as it was her voice that recorded the details for the second failed ransom drop, in Bathpool Park itself. On the tape she seemed calm and collected, given the circumstances. It is claimed that Neilson spotted a police vehicle in the area at the time of the second drop, and decided not to risk a police trap, aborting the ransom drop. Unbeknownst to the police, the second failed attempt ended just yards from the drainage shaft where Lesley was imprisoned, but no search of the immediate area was carried out at the time. Furious that his instructions had not been followed, Neilson waited nearby for Ronald Whittle and the police to leave, before entering the drainage shaft and killing Lesley Whittle in a rage. Had police conducted a thorough search before leaving, there was every chance they might have discovered Lesley alive.
On the same night as the last aborted drop, Neilson was also involved in a freight train terminal robbery, in which a security guard, Gerald Smith, was fatally injured. Forensic evidence again linked the crime to the “Black Panther” post-office heists, but no connection was made to the Whittle kidnap at that time. It took police more than a week to discover Neilson’s stolen getaway vehicle, which he had abandoned close to the terminal, in which tapes of Lesley Whittle’s voice, and ransom drop instructions, were found.
Finally making the connection between the “Black Panther” and Lesley Whittle, and given that 10 days had passed without word from her kidnapper, a proper search of Bathpool Park was instigated, and the news blackout, that had proved so ineffective, was lifted. A televised interview with Ronald Whittle, and public assistance, led to the discovery of Lesley Whittle’s body nearly two months later, on 7 March 1975.  She was discovered hanging naked from a rope tied to the end of a metal hawser in the drainage shaft, and post mortem evidence revealed that she had been killed within days of her kidnapping.