Junior Bradshaw and Kevin Liverpool have been convicted of plotting to kill British singer Joss Stone.
Junior Bradshaw, 32, and Kevin Liverpool, 35, both from Longsight, Manchester, UK, were found guilty of planning to rob and murder Joss Stone at her home in Devon.
Both men had travelled to Devon in June 2011 armed with weapons and notes detailing their plans to behead the singer.
Kevin Liverpool was jailed for life with a minimum term of 10 years and eight months at Exeter Crown Court.
Judge Francis Gilbert QC told the plotter: “It was your scheme.
“This may have been the crazy scheme of a crazy person… but it was a very real plan.”
The sentencing of Junior Bradshaw has been adjourned for psychiatric reports.
The jury took just over four hours to reach unanimous verdicts on charges of conspiracy to murder and conspiracy to rob.
Speaking outside court, Joss Stone’s mother Wendy Joseph said: “Joss would like to thank everyone for their support and all their good wishes.
“The whole family is relieved the trial is over and these men are no longer in a position to cause harm to anyone.”
Supt Steve Parker, Devon and Cornwall Police’s senior investigating officer on the case, said: “I’ve got no doubt that Liverpool and Bradshaw intended to harm Miss Stone and that without the vigilance of the public and the good work of our officers, they represented a serious threat to her.”
Junior Bradshaw and Kevin Liverpool set off from Manchester in the early hours of June 13, 2011.
Their Fiat Punto was laden with weapons including a samurai sword, hammers and knives.
When they arrived in East Devon they drove around for several hours attempting to find Joss Stone’s house, stopping to ask a postman for directions when they got lost.
Joss Stone, who grew up in the area, was at home at the time.
The men were eventually reported to police by suspicious residents in Cullompton.
When officers examined the car and found it full of weapons Junior Bradshaw and Kevin Liverpool were arrested and later charged.
Supt Parker said: “I am aware that as a result of this incident [Joss Stone] has reviewed her security arrangements, but I am sure she will continue to be a prominent and popular member of her local community.”
During the trial, the prosecution said notes written by Kevin Liverpool showed the accused wanted to behead Joss Stone and dump her body in the river because of her links to the Royal Family.
Joss Stone was a guest at the wedding of Prince William and Kate Middleton.
During sentencing, Judge Francis Gilbert told Kevin Liverpool: “It is clear from your text messages on your phone that from as early as November 2010 you had been planning to rob someone of what you hoped would be in excess of £1 million.
“By January 2011… you had identified Joss Stone as the target.
“You had no reason to target her except that she was a wealthy young woman as she was a successful singer.
“You assumed that as she was a friend of the Royal Family she would be able to give you money of that sort of amount.”
The judge also said Kevin Liverpool, whom he branded as “dangerous”, had recruited Junior Bradshaw into his plot.
He said he was considering passing a hybrid sentence on Junior Bradshaw, involving a custodial term which would most likely be served in a secure psychiatric unit.
During the trial the jury was told that Junior Bradshaw suffered from disorganized schizophrenia.
Giving evidence he said he had never heard of Joss Stone until his arrest and thought he was just on a day out with his friend.