High Court Judge Mr Justice Saunders jailed Docherty-Puncheon for life following the majority verdict.
Docherty-Puncheon had denied the allegation and claimed that he was at home nearby when Lt. Col. Workman was fatally shot in the body.
However, during the murder trial the jury was told that he later revealed facts about the murder to a cell-mate, while on remand over the disappearance of 21-year-old traveller Fred Moss.
"He described how the colonel was shot," said prosecutor Richard Latham QC in his closing submissions to the jury.
"How could he have possibly known that?"
The jury at St Albans Crown Court, Herts., was also told that he confessed to being a "modern day hitman" who had murdered Lt. Col. Workman for cash and revealed that his victim had been holding a walking stick and looked away when he was shot.
Mr Latham added: "He is someone who is capable of a cold blooded execution and who is capable of dismembering a body and disposing of it."
His fellow prisoner also told how homosexual Docherty-Puncheon, who was in a civil partnership, had claimed to have had a sexual relationship with the "wealthy" Lieutenant Colonel and that he had made the confessions as the pair watched a news report on the murder of Mr Moss.
Docherty-Puncheon also told his cell-mate - who cannot be identified for legal reaons - where he had hidden the weapon he used to kill Fred Moss.
That information eventually led police to discover the weapon, which had Moss' DNA on it, the jury heard.
The court was told Docherty-Puncheon became annoyed when his cell-mate questioned his confessions and began revealing details of the murder, adding that he had known the Lieutenant Colonel since 1998.
However, Docherty-Puncheon - who was also known as Christopher Nudds - said the cell-mate was lying and had made up "ridiculous stories."
Of the sexual relationship allegations, he told the jury that the rumours were like something out of TV show Midsomer Murders and that people made stupid jokes of Mr Workman being his "sugar daddy."
Docherty-Puncheon's Range Rover was spotted on the night of the colonel's shooting, the jury of six men and six women was told.
The vehicle was seen by a landscape gardener, who noted the unusual number plate of "S0H0" - actually N50H0, said Mr Latham.
Docherty-Puncheon maintained the witness was mistaken as he was at home when the brutal act was carried out and had not left until the following morning.
He was arrested by police soon after the killing, but released without charge.
Docherty-Puncheon denied the charges of murder and having a firearm with intent.
He said that he had carried out work in the area as a pest controller, including work removing wasp nests on the outside of Lt. Col. Workman's home.
His father was a gamekeeper and he had obtained a full-length shotgun when he started in his profession as a pest controller and had held a shotgun certificate since the age of 13 years.
The hearing was also told that Docherty-Puncheon's uncle, Peter Ward, had seen a sawn-off shotgun hidden under the seat of his nephew's Subaru before the murder of Mr Workman.
However, Docherty-Puncheon had maintained in evidence that his uncle had been "completely mistaken."
Docherty-Puncheon had initially been a suspect in the police investigation - which involved interviewing more than 3,000 people and the offer of a £10,000 pounds reward.
He was eventually charged in July 2010, following a cold case review.
During his 25-year Army career the Lieutenant Colonel, who served with the Oxfordshire and Buckinghamshire Light Infantry was stationed in Canada, Nigeria, Germany and Cyprus and travelled widely in the United States.
After retiring from the Royal Green Jackets in 1965, Lt Col Workman, a proud recipient of the Burma Star, had worked as an antiques dealer.
During the course of the investigation detectives revealed that Mr Workman had led a double life in the 1960s - as a respectable Army officer and as a practicing homosexual, which was still illegal.
He was married to Gladys Parker - known as Joanna - in 1968, and had been her full time carere from 1994 until she died just months before her husband's cold-blooded murder.
A well respected member of his local community, Lt Col Workman's memorial service was packed with villagers and even attended by Viscount Slim, son of Field Marshal Slim "of Burma".
Members of his family, including brother Cecil, lived in Australia but made repeated pleas during the police investigation for anyone with information to come forward. mfl ends
