Gardener Jean-Louis Cayrou has been found guilty of the premeditated murder of his British expat lover Patricia Wilson at her rural French home in 2012.
Cayrou, 54, was sentenced to 30 years in prison for killing Mrs Wilson, 58, following the collapse of their relationship, after the jury deliberated for almost five hours at the Cour d'Assises de l'Aveyron in Rodez, south-west France.
Gasps were heard from members of his family as he received his sentence, against which he has 10 days to appeal.
Mrs Wilson's mother, Jean Wilson, 84, said "justice has finally been done" following the verdict.
Cayrou is believed to have cut the electricity at Mrs Wilson's home near the village of Vabre-Tizac, in the Aveyron region, and killed her shortly after she returned from visiting her mother in England on August 17 2012.
Described as "dominating" and "unstable" in court, Cayrou left a trail of blood through the isolated house, leading down the steps outside, where he is believed to have loaded Mrs Wilson's body into his car.
Mrs Wilson's body has never been found and Cayrou's refusal to disclose where he hid it has been condemned by the prosecution.
In a written statement released following the verdict, Jean Wilson said she was "pleased that justice has finally been done" but said the result was "tinged with sadness" - as she would still have to live without her "perfect daughter".
She said she had been left heartbroken when her daughter, who was her "best friend" and "confidante", was "cruelly taken away".
"To lose a child is a devastating experience, but to lose a child in this manner, through an act of extreme violence is indescribable," the statement read.
"When her life was snatched away in such a brutal way, a large part of my own was taken away forever. Losing her was the biggest sadness of my life and has left a gap that can never be filled.
"I think about her and the terrible circumstances of her death every day. All I am left with are the fond memories of my loving daughter and the wonderful times we spent together. I will never forget her."
Mrs Wilson was originally from Welwyn Garden City, Hertfordshire, before moving to France with her partner Donald Marcus, 58, in 2008.
She embarked on a relationship with Cayrou, her gardener, in the spring of 2012. Mr Marcus had returned to England to seek medical treatment after developing the early symptoms of multiple sclerosis.
Mrs Wilson was initially happy with Cayrou, but he "turned into a jealous, possessive person, who wanted her to himself" and their relationship deteriorated, her friend Fiona McKinley, 61, told the court.
Her death came just weeks after she told friends that Cayrou had broken into her house in the middle of the night, climbed on to her bed and attempted to suffocate her.
Kieran Mitchell, a lawyer from Slater and Gordon representing Jean Wilson, described Cayrou as "heartless" and "lacking remorse" for putting Jean Wilson through the "added ordeal" of a criminal trial.
He said: "This was a brutal murder of an innocent woman whose only mistake was to have a brief relationship with the wrong man.
"Cayrou cruelly murdered her simply because she said she didn't want to be with him."
The court awarded 20,000 euros in compensation to both Jean Wilson and Mr Marcus for their ordeal and 8,000 euros each for legal fees.
Mr Marcus was also granted more than 15,000 euros in compensation for the damage caused to the home he had shared with Mrs Wilson and the time he could not spend there during the investigation.