Ronnie Biggs: Wants to come home to die

While some countries set an upper age limit beyond which convicted criminals cannot be held in custody, the UK has no such rule.

In special circumstances, the Home Secretary can decide to release a prisoner early.

This was how the East End gangster Reggie Kray came to end his days a free man, rather than behind bars at Wayland Prison.

Kray, however, was dying of cancer and had already served 31 years for the murder of Jack "The Hat" McVitie.

Grey area

Although the majority of the UK's inmates are under 30, the number aged over 60 has trebled in the past decade.

HM Prison Service figures show that in 1989, there were 345 prisoners aged over 60; by 1999, there were 1,053, of which 21 were over 80.

General Pinochet had been under house arrest

Although she escaped prosecution, fellow pensioners were not so fortunate.

In 1999, Anthony Sawoniuk, 78, was given a life term following the UK's first full Nazi war crimes trial.

Later that same year, Sandor Bata, 75, got life for murdering a fellow pensioner after a row about clematis cuttings.

And Stanley Casson, 90, became the UK's oldest prisoner when he was jailed for causing death by dangerous driving. His sentence was soon quashed on appeal.

Life means life

The trend towards an ageing prison population is, in part, due to the fact that people are living longer.

Serving life: Wheelchair-bound Sandor Bata

In the United States, severe sentencing policies of the 1980s and 1990s (such as a greater reliance on mandatory life sentences) have already had a major impact on the prison population.

In Ohio, the state predicted in 1995 that it would need 3,000 beds for elderly convicts by 2003. It reached that within two years.

Some states, such as Virginia and Pennsylvania, have prisons dedicated to elderly inmates. These include facilities to help the frail, and often have more relaxed security.

The UK has only one small unit designated for older prisoners, at HMP Kingston, in Portsmouth. It houses around 40 inmates, but all must be mobile.

The Prison Service is now spending �3m on creating facilities for elderly inmates at several prisons.

Could just such a facility be the place where the ailing Ronnie Biggs sees out his days?