The cause of prevention and early intervention continues to bob to the surface of UK politics, generally within eyeshot of the cross-party alliance between former Conservative party leader Iain Duncan Smith and Nottingham North MP Graham Allen.

Both men gave evidence to the Home Affairs Committee on youth crime whose report this week acknowledged an increasingly familiar argument in favor of long-term investment in prevention.

The main cost-benefit message was translated by the BBC into the headline “Prison for a child is said to be almost five times the cost of a year at Eton” – Eton still being regarded as the sitting-duck emblem of British social and educational privilege.

That calculation was based on the “key factor” that a young person in the UK criminal justice system cost the taxpayer on average over £200,000 by the age of 16, whereas one given support to stay out cost less than £50,000.

Other “key factors” were arguably more arresting. For example:

• putting pressure on the car manufacturing industry to design out opportunities for crime had contributed to a 65% reduction in vehicle theft since 1995

and

• the introduction of Chip and PIN technology reduced losses on transactions on the UK high street by 55% between 2004 and 2008

underlined by

• young people exposed to the most acute combination of risk factors – which include family neglect, poverty, school under-achievement and a lack of positive role models – were between five and 20 times more likely to offend than those who are not

and

• good resettlement support can reduce the frequency of re-offending by 35% and the seriousness of re-offending by 10%.

The committee said the government had been too slow to put more effort into creating an early warning system from crime statistics so that experts could better identify emerging trends. Short custodial sentences made effective rehabilitation "almost impossible".

The chairman, MP Keith Vaz, said: "It may seem a bit of a truism now, but the fact is that when it comes to preventing crime, all the value for money comes from investing in communities, in social programs, in activities and mentoring for young people, in health, in technology - rather than spending on the criminal justice system.

"This government has been tough on crime but not tough enough on the causes of crime.

"It is clear that prison, and especially short custodial sentences, do little or nothing to prevent offending or aid rehabilitation. And yet, perhaps because of lack of investment, alternatives to custody are not yet working properly."

Graham Allen was in similar action earlier this month, pressing the UK Minister for Children, Young People and Families, Dawn Primarolo, for news of an anticipated Green (policy proposal) Paper on early intervention.

Something would be arriving shortly, she told him, to help local authorities and their partners, working in children's trusts and elsewhere, to improve the quality and consistency of the support that they offered to vulnerable children and families.

Did she agree with him that a social and emotional bedrock was the foundation of all attainment for babies, children and young people, and that the government should continue to support it and ensure that it was spread as far as humanly possible, particularly in deprived constituencies such as his?

“Not only do we know that shifting to early intervention can provide value for money, in terms of the costs to the individual, the family and the community at a later stage,” she said, “but the evidence base clearly shows that intervening early is a particular help to children's development and their ability to learn.”

See also: UK treasury sold prevention with a money-back guarantee

• For Ian Jack's illuminating investigation and reconstruction of Jimmy Sime's 1937 photograph of Harrow public schoolboys outside Lord's cricket ground, see The Guardian Online and also the full version of his essay in the spring issue of Intelligent Life magazine .