A thug who slaughtered a “gentle” 18-year-old friend before dumping his body in a ditch has failed to convince a top judge his good behaviour behind bars merits a cut in his sentence.

Steven Knott, of Didcot, was just 16 when he and Leon Paige, also 16, plotted the murder of Richard Parker who they believed had “grassed them up”.

Richard died “very rapidly” after the pair he considered his friends laid into him with bottles and a knife in a village lane.

His body was found four days later in a ditch under a sleeping bag. Knott, now 24, and Paige, were convicted of Richard’s murder in June 2002 and both were put behind bars for life.

They were told they must serve a minimum of 12 years behind bars before they would even be considered for parole.

At the High Court in London, Knott’s lawyers argued that “tariff” should be cut to reflect what they said was his “exceptional progress” in custody. They pointed to a wealth of positive reports from prison, where he has completed numerous courses and finally accepted his role in Richard’s murder.

But, in refusing to cut his 12-year tariff, Justice Nicola Davies said: “I cannot conclude that there is evidence of exceptional progress in prison, nor of a risk to the continued development of Steven Knott within the custodial setting.”

The decision means Knott will not be able to seek parole until January 2015 and, even then, he will only be released if he can convince the Parole Board the danger he poses to the public has passed.