Peter WalshThe son of Great Train Robber Ronnie Biggs has told how his dying father, who celebrated his 80th birthday on Saturday, is likely to remain in hospital for at least a week.Peter Walsh

The son of Great Train Robber Ronnie Biggs has told how his dying father, who celebrated his 80th birthday on Saturday, is likely to remain in hospital for at least a week.

Michael Biggs, 34, spent the day with his father at the Norfolk and Norwich University Hospital on the train robber's first day of freedom after justice minister Jack Straw agreed he could swap his jail cell for a hospital bed on compassionate grounds.

His prison sentence ended when paperwork was completed at around 2pm on Friday.

Biggs, who has been described as 'extremely weak' and unable to swallow or speak, is in hospital being treated for pneumonia.

But despite his father's illness, it was still a happy day for son Michael who himself celebrates a birthday - his 35th - next Sunday.

'He's extremely frail and weak, but very happy,' said Michael Biggs.

As part of the celebrations, which fell on the 46th anniversary of the robbery, Biggs was given a card and balloons - one of which said 'Happy Birthday Ronnie' in his bed.

'The doctors are keeping him stable - he's sleeping most of the time,' added Mr Biggs. 'He's due to have surgery on Tuesday. We can't really think about him leaving hospital at the moment.

'I would think he'll be here at least this week.'

Mr Biggs said that his father would then 'be retreating fully from public life' and would not be at the centre of a 'media circus'.

If he is well enough Biggs, who was moved to the hospital from Norwich Prison last week, could be moved to a nursing home after his stay in hospital.

Biggs spent 30 years on the run after being part of a 15-strong gang which stole �2.6m from the Glasgow to London mail train at Ledburn, Buckinghamshire, in 1963.

He was given a 30-year sentence but escaped after 15 months and lived in Australia and Brazil - where Michael Biggs was born.

Biggs, from Lambeth, south London, returned to the UK voluntarily in 2001 and was sent back to prison.

Since then his health has deteriorated and he has suffered a series of strokes.