THE blue lights twinkle and the sirens cry out as Durham Constabulary’s night-shift cops race to the 617th call of the day. Yet they do not pull up at the scene of a stabbing or a pub brawl, but outside a mental-health hospital. It is familiar turf: police were summoned earlier that day when a patient went missing. He was eventually found, popping to the gym. Now another patient has wandered off, a 20-something woman who lives 50 miles away but is staying here because of a lack of beds in her hometown. The police find her, on another ward, and coax her back to her room. How did she slip out? “To be honest with you,” a nurse says, “it’s because we’re running on low.”

The police have always had a wide remit. Egon Bittner, a sociologist, once defined policing as responding to “something that ought not to be happening and about which someone had better do something now”. But there is evidence that demands on front-line cops are becoming broader. More than four-fifths of the calls they receive are not related to crime, according to a report in 2015. The Metropolitan Police responds to a mental-health call every 12 minutes, an increase of a third in five years. Over the five fiscal years to 2016, the national number of reports of missing people jumped by 16%.

Shifting expectations may partly explain rising demand. Cops must respond to changing public priorities to maintain their legitimacy, argues Rick Muir of the Police Foundation, a think-tank. They adapted to concern about antisocial behaviour in the 2000s. Now there is more awareness of mental health and greater concern about missing children, following a series of sexual-abuse scandals.

Another explanation is that budget cuts have shifted demand from other public services. The number of mentally ill adults has grown steadily over the past 25 years, but there are 12% fewer mental-health nurses than there were in 2010. Funds for ambulance services have risen, but not by enough to keep pace with demand. The police often pick up the slack. In one case, they spent 20 hours with a woman who had left a psychiatric hospital three times that week before medics could assess her. Calls spike at 5pm on Fridays, when social workers hand over their caseloads. “People don’t just get into crisis in office hours,” grumbles Sir Tom Winsor, the chief inspector of the constabulary, who wants other services to work in the evenings and at weekends.

Coppers tend to be poorly equipped for their new roles. Police budgets have also been chopped. There are 14% fewer police officers than there were in 2010. Those who remain are hardly mental-health specialists. Most on the Darlington night shift say that they spent half a day of their 13-week initial training on the topic (the College of Policing now recommends at least two days). “I was a mechanic,” says one. “They’re looking at me, saying ‘Help me’. It can be tough.”

Uniformed cops can also aggravate a mental-health crisis. And the gap between recruits’ expectations and the reality of what they end up doing risks damaging morale and breeding cynicism, says Sarah Charman of Porstmouth University. After five weeks in the job, three-quarters of recruits whom she studied said their primary purpose was fighting crime. After four years, only about 40% thought so. Recent reports that remarkably few crimes are solved will not help.

But some forces are adapting. Mental-health nurses have been working in some police call-centres since 2013; others travel to incidents with cops. They can obtain medical data and advise officers on how to respond. The scheme has led to significant falls in compulsory mental-health detentions by police in some areas. A handful of forces are taking an even more radical approach, attempting to tackle the causes as well as the consequences of the demand. Durham Constabulary finances a charity that organises football matches and litter-picking. It has restored a fishing boat for locals and turned a vacant allotment into a vegetable patch. Mike Barton, the chief constable, says he is happy to spend his budget improving neighbourhoods so that they look after their own needs. “If it is going to be our problem later on, we may as well deal with it.”