FROM the start today, we'll admit that we have no firm answer to the question posed by the suggested return of Ronnie Biggs to Britain.

If reports are correct, after 35 years on the run, the frail Great Train Robber has sent an e-mail to Scotland Yard detectives saying: "I'd like to give myself up to you."

The question's the one which preceded the release of gangster Reggie Kray, and it's one which has - and will again - echo round the nation over Moors murderer Myra Hindley.

It's this: Whether you believe that a prison sentence is about retribution, and nothing else, or whether your view is that rehabilitation plays its part, at what point is it right for society to switch from extracting a debt to investing in compassion?

In Kray's case, he was released from a life sentence because he was close to death from cancer.

There were some people who'd have seen him rot in jail, but it's arguable that society - thus, all of us - gained more from being civilised, and demonstrating it, than by continuing to be vengeful.

He wasn't capable of reoffending, but he did breathe free air again. There's the dilemma.

Biggs suffered a stroke in 1998, something which left him partially paralysed and affected his speech.

He knows his days are numbered but, although he's prepared to fly back to the country and take whatever the law dishes out after he steps out of Arrivals, is it worth taking up a prison cell with a 71-year-old who, theoretically, could remain behind bars until he's 100?

The answer will define much about Britain and the way it sees itself in the early 21st century.

That may not sound important now. Nothing about the Biggs story might strike you that way.

But the moral maze will take its most twisting turns when Hindley begins to feel the hand of death. It's as well to have our thoughts prepared.