Two men convicted of plotting to rob and kill international pop star Joss Stone have won challenges against the length of their sentences.

Junior Bradshaw, 33, had his 18-year sentence cut to 10 years by three Court of Appeal judges in London.

Kevin Liverpool, 36, who was originally given a life sentence with a minimum term of 10 years and eight months, had his minimum reduced to six-and-a-half years.

The pair were found guilty of conspiracy to murder and conspiracy to rob following a three-week trial at Exeter Crown Court last year.

They drove from Manchester to Joss's home in mid-Devon with an arsenal of weapons to rob and kill her.

When the pair were sentenced, Judge Francis Gilbert, the Recorder of Exeter, branded Liverpool a danger to the public and said he targeted Joss to get more than £1 million from her.

He told him: ''You intended to rob her and kill her and dump her body in the river, according to your words, and then leave the country with your accomplice, Junior Bradshaw. You had no reason to target her except that she was a wealthy young woman as she was a successful singer."

Liverpool and Bradshaw had scouted the singer's home and were on their way to attack her armed with a sword, three knives, two hammers, masks, gloves and a hosepipe when they were arrested in Cullompton in June 2011.

Suspicious residents had called the police, having spotted their badly-damaged Fiat Punto in the area.

The pair told police they were lost and were trying to get to Bristol but officers became wary and quickly discovered the cache in the boot.

Giving the ruling of the court, Mr Justice Bean said it had dismissed Liverpool's appeal "insofar as it challenges the imposition of a sentence of life imprisonment".

 It had been argued on his behalf that the "clumsy and badly-planned" conspiracy was not so serious as to qualify Liverpool for a life sentence.

The judge said the court "cannot accept this submission". It was a conspiracy to murder using an "array of weapons", and was persisted in even after the setback of damage to their car.

He added: "When coupled with the finding that the appellant (Liverpool) poses a high risk of serious harm to the public, it leads to the clear conclusion that a life sentence was justified."

Taking into account the 22 months spent in custody before sentencing, Liverpool becomes eligible to apply for parole in December 2017.

But the judges stressed that "we are not ordering that the appellant be released in December 2017".

Mr Justice Bean emphasised: " Far from it. The significance of the minimum term is that it specifies that the Parole Board will only be able to consider for the first time in late 2017 whether the appellant can safely be released.

"The assessment of future risk is a matter for the Parole Board and not for this court. We have already noted the many references in the reports on Liverpool to the need for him to be observed for a substantial period of time before a conclusion can be reached on the level of risk which he poses.

"The purpose and effect of a sentence of life imprisonment is that if it is never considered safe for the offender to be released, he may remain detained for life, and that if he is ever released it can only be on licence and subject to supervision."

Turning to Bradshaw's appeal the judge said he was "of exceptionally low intellectual capacity".

As the trial judge had noted, Liverpool was the instigator and Bradshaw was the foot soldier.

Mr Justice Bean said that had he been more intelligent "he would have realised that the chances of a successful and profitable robbery were so remote as not to be worth attempting".

In the light of the reduction made in Liverpool's minimum term, and the trial judge's finding "which was clearly correct", that Bradshaw was to be treated as a foot soldier, "a reduction in his sentences should likewise be made".