Our Prisons are full to bursting point, and provide short sentences provide little in the way of deterrence, all whilst at the same time costing mr. and mrs. taxpayer £1000's to keep them in boxes, doing nothing.
The Scrapping of National Service was a cynical effort on behalf of the PC brigade to make us a more progressive society, which is fair enough. But unfortunately the PC brigade forgot that society only understands good discipline when it instilled into it by insitution. (Even if a bit heavy handed)
Schools no longer provide discipline, so this can't be relied upon to instill the values into todays youngsters.
Introducing national service for 18+ year olds who are not in higher education or persistently unemployed would cut down on "yobs" on the streets, and give those a chance to learn new skills in the armed forces that can be transferred to civilian life when they leave, greatly increasing their chances of a well paid job to provide for themselves.
Bringing it back as a punishment for petty crime such as theft — keeping criminals separate of course — would again allow rehabilitation of offenders by instilling forced discipline upon them, and making them once again useful to society.