London  - The family of Britain's "Great Train Robber", Ronnie Biggs, Thursday reacted angrily to the government's decision to keep the frail 79-year-old in jail.

British Justice Secretary Jack Straw Wednesday ruled that Biggs, who was convicted in 1964, escaped and spent 36 years on the run from police, should serve the remainder of his sentence as he had been "wholly unrepentent."

"This is not justice. This is beyond belief," Biggs' son Michael said. His father was in a "life-threatening condition" and "no threat to society whatsoever."

Biggs was a member of a 15-strong gang which raided the Glasgow to London mail train in August, 1963, and made off off with 2.6 million pounds, a record at the time and dubbed in Britain "The Great Train Robbery."

He was given the 30-year sentence but after 15 months he escaped from prison in London and went onthe run, living in Spain, Australia and Brazil.

Biggs, who returned from Brazil in 2001 to give himself up to British police, is currently in hospital in the eastern city of Norwich after breaking a hip. He had earlier been held in jail there.

Straw ruled that he should not be granted parole, despite a recommendation to the contrary from the prison parole board which considers the release of convicts after they have served about a third of their sentence. The date for Biggs' release would have been Friday.

Biggs's son, who was due to visit his father Thursday, said the hospital had confirmed to him that his father was in a "life-threatening" condition.

"If this is the British legal system, it is appalling, it's beyond comprehension. I hope that Mr Straw finds it in his heart to review his recommendation not to release my father."

Biggs became a celebrity whilst on the run in Brazil, starring in a film with the punk band The Sex Pistols. (dpa)