It seems that any hope the police had that events in Paris may have won them a last minute reprieve in the Spending Review has been dashed. The Chancellor was clear over the weekend that while the counter terrorism budget would be increased he did not buy the argument that overall cuts to police budgets will put the country at greater risk in the event of a terrorist attack. The IFS has set out just how brutal these cuts could be, estimating that non-protected departments such as the Home Office face a cut of 27 per cent when the Spending Review is announced on Wednesday.

If we see cuts of this scale what is likely to be the impact? It is important first of all to remember what has happened so far. Between 2010/11 and 2014/15 police grants from central government fell by 20 per cent. Taking into account local council tax revenues this means that police spending in total fell by 14 per cent.

So far the cuts have largely been absorbed through efficiency saving such as reorganising neighbourhood policing, improving the efficiency of call centres, closing police stations, reducing procurement costs and freezing recruitment. Between 2010 and 2014 this meant a 12 per cent fall in the number of police officers (16,659), a 25 per cent fall in the numbers of PCSOs (4,150) and a 20 per cent fall in the number of police civilian staff (15,918).

Although some further cuts could be absorbed without a major impact on frontline services, cuts on this unprecedented scale will impact on the quality and scope of the policing the public will experience. This is because 79 per cent of police spending is made up of staff costs and the vast bulk of that in turn is made up of police officer salaries. It is inconceivable that these cuts can be made without a significant further reduction in officer numbers, with forces already planning to cut a further 7,400 officers by 2018 and with the final number up to 2020 likely to be much higher.

What will this mean for our model of policing? It is important to note that the impact will vary from area to area, because of the different priorities of elected Police and Crime Commissioners and because of the different way police forces are funded. Some, such as Surrey, Dorset and North Yorkshire, receive almost half their funding from local council tax payers, which gives them some protection from uniform cuts to central government grant if that is how the Home Office chooses to proceed. Others such as Northumbria, the West Midlands, Merseyside and Greater Manchester get over three quarters of their funding from central government and less than a quarter from council tax payers, leaving them particularly exposed.

However, the following trends are foreseeable. Cuts to officer numbers are likely to require more than simply ‘natural wastage’ and a recruitment freeze, meaning there will be a major debate about introducing compulsory redundancy for police officers. This has historically been seen as a threat to the independent status of the office of constable but is starting to look inevitable if cuts on this scale are to be achieved.

There will be a significant further paring back of neighbourhood policing and in some areas regular visible police patrol of the kind that has been prioritised since the mid-2000s may all but disappear. The government will claim that there is no link between random foot patrols and reductions in crime – and they are right. Nonetheless most evidence shows that targeted foot patrol can have an impact on crime and that the introduction of more visible neighbourhood policing has led to improvements in public confidence in the police. We know from the Crime Survey for England and Wales that the visibility of police foot patrols has been falling since 2010/11, and that visibility is positively associated with how the public rate their local police.

The proactive and preventative work that neighbourhood policing facilitates by allocating teams of officers to a particular patch will be replaced by a retreat to response policing, with officers having to make more and more difficult decisions about which incidents to prioritise. The public are likely to see response times get slower and it may become more and more difficult for the police to attend non-priority incidents, such as attempted burglaries for example.

There will have to be a major debate about the police role in responding to non-crime incidents. These make up 83 per cent of reports to police Command and Control and include for example complaints about noise nuisance, incidents involving people with mental health problems and reports of missing people. One of the challenges for the police is that because they are a 24-hour service and because one of their core competencies is emergency response they are likely to be called out in crisis situations when other services are unavailable. This means they will often be left ‘holding the baby’ as other agencies such as social services and mental health services are cut back.

What is harder to tell is whether in some areas the level of financial stress may put some forces over the line in terms of operational viability, being unable to provide the basic response and statutory duties to an acceptable standard. HMIC has highlighted Bedfordshire, Cleveland, Dorset, Dyfed-Powys, Lincolnshire and South Yorkshire in particular for concern in terms of the sustainability of their finances. The Bedfordshire Police and Crime Commissioner has even written to MPs from neighbouring forces warning that they may have to take over his force in the event that it becomes financially unviable.

These concerns have exposed the lack of an ‘early warning system’ of shared indicators that would enable us to identify forces that may be at risk of becoming financially unviable. We also lack a common understanding of how many officers are required to maintain operational viability or a ‘safe level of policing’. The need for such a shared understanding is becoming ever more pressing.

As is the need for an acceleration of the kind of inter-force collaboration we have seen for instance between West Mercia and Warwickshire where the forces have for operational purposes effectively merged. As the National Audit Office has demonstrated, the planned savings to be made from collaboration vary markedly across forces from 0 to 47 per cent of planned savings in 2014-15. Our current structure of 43 territorial polices has never looked more unsustainable.

The police service in England and Wales faces perhaps the biggest challenge in its nearly 200-year history. Austerity is reducing resources available to an unprecedented degree, while the changing nature of crime (in particular the rise of internet crime) is challenging the whole model of policing. The worst response to this challenge would be a piecemeal one. Rather the police need to start asking what they are for, what crimes and harms they should prioritise, and what their skills and expertise can contribute to tackling them in partnership with other public services and the wider community. The police, in short, face an existential moment.