The mulberry bush of the nursery rhyme was really a tree - in the yard of Wakefield prison. Prisoners used to walk around it for hours at a time before being led back to their cells. So the expression 'here we go round the mulberry bush' came to mean getting nowhere, or an exercise in futility - a perfect description, some would say, of prison itself.

Today there is almost complete agreement among penologists that for most prisoners, prison simply doesn't work, doesn't deter, doesn't reform and costs too much money. Why then, when most other countries are closing prisons down, is Britain building more?

Michael Dean and Harold Williamson talk to the men who make up the overwhelming majority of our prisoners. Not dangerous criminals but social casualties.