[4] Neilson served in the British Army and was posted in Kenya, Cyprus and Aden as part of the King's Own Yorkshire Light Infantry.

After stealing guns and ammunition from a house in Cheshire, he escalated his criminal activity, turning to robbing small post offices.

Neilson was linked to the post office shootings after he shot security guard Gerald Smith six times while following a ransom trail.

A series of police errors and other circumstances resulted in Whittle’s brother, Ronald, being unable to deliver the ransom money at the designated time and place demanded by the kidnapper.

[13][14] Lesley Whittle's body was found on 7 March 1975, hanging from a wire at the bottom of the drainage shaft where Neilson had tethered her in Bathpool Park, Kidsgrove, Staffordshire.

Others theorized that Neilson panicked and fled on the night of the failed ransom collection without returning to the shaft, and that Whittle may have been alive for a considerable period of time before she fell to her death.

The pathologist noted that Whittle weighed only 98 pounds (44 kg) when found, her stomach and intestines were completely empty, she had lost a considerable amount of weight, and was emaciated.

[16] In December 1975, police officers Tony White and Stuart Mackenzie, stationed on a side road off the A60 in Mansfield, encountered Donald Neilson, who was carrying a holdall.

The gun discharged, causing a minor injury to White’s hand, while Mackenzie exited the car and called for assistance.

During Neilson's trial at Oxford Crown Court, his defence barrister, Gilbert Gray, contended that Whittle had accidentally fallen from the ledge, and died as a result.

For instance, he asked the jury whether they believed any hangman's noose would be padded and lagged with 77½ inches of Elastoplast to avoid chafing, or that any scaffold would be cushioned with a rubber mattress and sleeping bags.

He asked the jury why Neilson bothered to keep her alive once he had recorded the ransom messages, arguing he could have simply clubbed her to death, and hidden the body in woodland.

Gray finished his speech by opining, "I submit that when Lesley Whittle went over the platform, it was an unlooked-for misadventure, unplanned and undesired.

[10] He was assessed by expert witness Lionel Haward, a forensic psychologist, and was found to be "suffering from a psycho-pathological condition of some severity" but not to the extent that it resulted in diminished responsibility.

Three further sentences of 10 years each were imposed for the two burglary charges when he stole guns and ammunition, and for possessing the sawn-off shotgun with intent to endanger life.

Neilson's defence team, solicitor, Barrington Black, junior counsel, Norman Jones, and leading counsel, Gilbert Gray, all claimed that his conviction was a reflection of public opinion, a backlash of the publicity given to the hunt for the kidnapper and killer, and that he should have been convicted only of the lesser charge of manslaughter.

Irene Neilson was later convicted of cashing over eighty stolen postal orders obtained during her husband's post office raids.

Her solicitor, Barrington Black, placed the blame squarely on Donald Neilson’s complete domination of his wife, describing him as a "Svengali, who had exercised a hypnotic influence".

"[citation needed] The solicitor said he felt this portrayal was confirmed by Donald Neilson when he had visited him in his top security cell.

The QC told the judge, sitting with two magistrates, that he was anxious that the court should be aware of the pressure and constraints placed upon Irene Neilson as a result of her husband.

Following subsequent legal judgements in various other cases, and the implications of European Union Human Rights laws, Neilson was repeatedly confirmed to be on the Home Office's list of prisoners with whole-life tariffs.

On 12 June 2008, Mr Justice Teare upheld the whole-life tariff and imparted:[22]This is a case where the gravity of the applicant's offences justifies a whole life order.

A fictionalized account of the Whittle kidnapping and Neilson's trial forms the basis of Adam Mars-Jones's short story "Bathpool Park", which attempted to show how the court and judge had "missed the point".