Ronnie Biggs has served two years of a 30-year jail term

The 74-year-old has been taken to Queen Elizabeth II Hospital in Woolwich, south London, after vomiting and becoming dehydrated.

He had been returned to Belmarsh high security jail in London on Wednesday after treatment for pneumonia.

His son, Michael, 29, said he had been "absolutely appalled" when told his father had been returned to the prison.

Very ill

He said: "When I saw my father yesterday he was in an extremely frail condition.

"They took him away before I could even see him again.

"He is very ill and the last place he should be is a Category A prison."

Biggs was said on Wednesday to have been left "very weak and very frail" by his illness and it was initially thought he had suffered a heart attack.

Biggs was caught and jailed for his part in the infamous �2.6m heist on a Glasgow-to-London night mail train in 1963.

He escaped from Wandsworth Prison in 1965 and fled abroad, becoming a Brazilian citizen and spending most of his time in Rio de Janeiro.

Appeal dismissed

He had been held in Belmarsh since he returned voluntarily to the UK in May 2001 - 36 years after escaping from jail and fleeing abroad.

His bid to appeal against his 30-year jail term was dismissed in October.

A High Court judge said Biggs' case was "hopeless" and "completely misconceived".

His lawyers are considering an application to the European Court of Human Rights.

Biggs has already suffered two minor heart attacks since returning to the UK, and had three strokes and two epileptic seizures.