A murderer's plot to escape from jail by helicopter has been foiled by prison guards and the police.
Brian Lawrence, 67, from Berkshire, planned to escape from Parkhurst last week using helicopter flights at the Isle of Wight Festival as cover.
He communicated with his accomplices using lemon juice as invisible ink and codes hidden in sudoku puzzles, the Ministry of Justice (MoJ) has revealed.
Lawrence is serving life for murder and for plotting two further killings.
The MoJ said he drew maps and gave encrypted instructions for his plan to bring a helicopter into part of the prison grounds not protected by nets.
It is believed Lawrence targeted the festival as members of the public would be less suspicious of a helicopter due to the air movements associated with the music event.
He intended to fund the escape using the sale of a quarry in Newbury, Berkshire, then flee to Spain.
The plot was uncovered when prison guards spotted the phrase "more heat, less light" in one of his letters.
They then found the invisible messages, which can be seen when the paper is heated from underneath.
Lawrence, who was jailed in 2005 with a minimum tariff of 21 years, has been transferred to another prison.
Barry Greenberry, governor of HMP Isle of Wight, which is an amalgamation of Parkhurst, Albany and Camp Hill prisons, said: "I am delighted at the way our security team and Hampshire Constabulary have foiled a possible escape attempt.
"I am very proud of the operations team at HMP Isle of Wight who diligently pieced together intelligence to stop a security breach.
"This is exactly the sort of excellent public service that the police and prison service provide to protect the public and reduce reoffending."
Lawrence, a retired schoolteacher, was found guilty at Reading Crown Court of battering a friend of his ex-lover to death.
He killed Deryk Cox, 69, before setting fire to his house in Caversham, Berkshire, in 2003.
He then set out to hire someone to kill two other people, but was caught when an undercover policeman posed as the hitman.
The trial heard that Lawrence had become "insanely jealous" of other men close to his married ex-lover after their three-year affair ended.
Parkhurst lost its maximum security status after three inmates escaped in 1995.