A murderer's plot to escape from a Secluded British jail using a helicopter and secret codes hidden in Sudoku puzzles has been foiled.

Brian Lawrence schemed to bring an escape helicopter into the grounds of a prison on the Isle of Wight, communicating with accomplices using lemon juice as invisible ink and encrypted instructions.

The 67-year-old retired teacher is serving a life term for killing a man and hiring a "hitman" to kill two others in 2003.

The Ministry of Justice said prison guards became suspicious when they spotted the words "more heat, less light" in a Lawrence letter, then found the invisible messages by heating the paper.

The ministry declined to say when the plot was foiled, but Lawrence has been transferred to another prison.

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