The atmosphere in the custody area at wood green police station in north london is intimidating. noise from angry detainees echoes off the hard surfaces and a gate of metal bars marks the entrance to a corridor lined with sparse, unfurnished cells.

It must feel equally menacing for a parent or guardian summoned to accompany an arrested child.

But, since early august, some guardians attending this and two other police stations in the capital have been offered extra support as part of a scheme designed to develop evidence of which tactics are truly effective in fighting crime.

In a consultation room they can watch a slick, professionally produced video that reassures them they are not alone and describes the experience of people who managed to find a route away from crime. at the end, they are handed a card with tips on talking to the children and contacts for support groups.

The initiative stands out because participants are selected by a computer system in what is one of the largest scientific, randomised control trials in uk policing.

Once the trial finishes around christmas, officers will study the future arrest rate of children whose guardians were offered the support. they will compare the figures six and 12 months after the trials conclusion with the statistics for the other children. if the technique is shown to work, it may be adopted across londons metropolitan police.

The trial is one of several being developed in london. others include an initiative to offer advice to victims of repeat burglaries to secure their properties and a scheme to mount intensive patrols in places where violence is likely at the highest-risk times.

They are putting the met at the forefront of a worldwide movement of police officers and academics pioneering an approach known as evidence-based policing. theapproach, originally developed by lawrence sherman, an us academic, in conjunction with some us police forces in the1990s, has been inspired by drives to bring more rigorous analysis to education and the practice ofmedicine.

Simon ruda, senior director of home affairs programmes at the behavioural insights team, a consultancy that advises on how to nudge peoples behaviour, said such trials should help police forces make better decisions.

Mr ruda has been seconded to work with the mets strategic insight unit, which works on evidence-based trials and uses internal met data to fine-tune operational plans.

Evidence-based policing is really an attempt to bring the most relevant attributes of academic rigour to policing, he said.

Suzanne hopper, an acting superintendent who helped devise the scheme, said the idea came from a sergeant in the custody suite at wembley.

We were looking at how we could use some form of evidence base to try and reduce reoffending in children, supt hopper said. [we asked], is there an opportunity whereby we could engage with the parent and offer them a bit more support and highlight some areas around procedure or spotting signs of potential changes in their child?

The question is how far extra rigour can help uk police forces deal with the problems they face after a decade of public spending cuts that left them grappling with substantially increased volumes of emergency calls and much lower staffing levels.

Adam elliott-cooper, a policing researcher at greenwich university, said the solutions to rising levels of some forms of violence and other crime lay beyond policing.

I think theres little point saying to a parent, we have this programme for you, if their child has experienced trauma and they have no access to mental health provision or if the youth club on the local council estate was closed and they have nowhere to go, he said.

Advocates of evidence-based policing nevertheless insist that careful, evidence-based trials could revolutionise uk policing. prof sherman, now director of the police executive programme at cambridge university, likened the potential change to the introduction of air-traffic control in aviation compared with when pilots flew by sight and maps.

Prof sherman said at least half a dozen forces were developing or running evidence-based trials. there is widespread international interest in the technique, especially in new zealand, whose national police force set up an evidence-based policing centre in 2017.

Its helping to provide much more hands-on guidance, prof sherman said.

Mr ruda said evidence-based trials should ensure forces were able to discover far more quickly which new policies worked.

This is a way of finding out exactly what is the effect, what is the return on investment, in a more and more rapid way, he said.

Mr elliott-cooper said such thinking merely created the illusion of progress.

It can create the illusion that the police are doing something other than simply punishing people, he said.

However, prof sherman insisted rigorous analysis could steer policing away from traditional techniques such as stopping and searching large numbers of young people. it might instead encourage forces to invest in better mental health services for disturbed individuals and rehabilitation, for which there is stronger evidence of successful intervention.

If they can scale this up, if they can develop alternatives to conventional wisdom...there are many other ways of preventing crime, prof sherman said of the mets trial programme.

Supt hopper, meanwhile, insisted evidence-based policing could allow her force to serve the public better.

Our resources are precious to us at the moment, so we need to feel were putting them in the right places, she said. its all about reducing the number of victims. thats what this is about.