The debate on police numbers this week demonstrates the changing terms of debate

Brexit has created many political casualties already. Whether directly, like David Cameron, or indirectly, like UKIP, the vote to Leave the EU has cut a swathe through the personnel, policies and priorities of the political classes. We can expect many more to fall victim to the process before it ends.

However, where there’s chaos, there’s opportunity. Jeremy Corbyn (ironically, the last surviving GB party leader from the pre-Brexit era) has been busy taking one very significant such opportunity, namely to go a long way towards redefining Britain’s domestic political and economic consensus.

You might well not have noticed that and with good reason. Both the government and the media have been obsessed with Brexit over the last three years – justifiably so. It’s the biggest single policy challenge a UK government has faced in at least one decade and perhaps several. With so much of the PM’s time being taken up managing Britain’s withdrawal from the EU, virtually no other reform is going through: ministers are simply managing their briefs and even then, Brexit is occupying a lot of their time.

Also, as has been painfully obvious this last month, Labour has more than enough of its own internal difficulties and that’s been blocking out media time for the party, talking about antisemitism, defections and infighting rather than the subjects Corbyn and co would prefer, much to his annoyance.

One side-effect of that media and government distraction is to reduce news coverage of non-Brexit politics to a series of incidents, often where things have gone wrong or where there’s some scandal or concern. This week, knife crime was the issue that broke through.

What was notable about the debate in terms of the contest between the parties and their ideas is that once again the case was made for more spending much more effectively than the rationale for previous cuts.

Whether because it’s distracted, because it’s complacent or because it’s lost interest in the reasoning, the Conservative government is proving far less effective in justifying the need for past spending restraint than it used to be. Theresa May’s comment that there was no direct link between police numbers and knife crime might be right – the issue is far more complex than that and if there was such a simple link, you’d expect all types of crime to be rising in line – but without putting in the intellectual leg-work to explain why (and she didn’t), it sounds too counter-intuitive to be believed. And in any case, there is a half-truth in the allegation.

But police cuts, the spending restraint that necessitated them, and fixing the public finances appear to be seen by No 10 as yesterday’s problem and yesterday’s debate (indeed, to a large extent they are: were it not for the risks of Brexit, the austerity program has succeeded in its mission to get the deficit under control and could be entirely ended now). May is clearly uninterested in rehearsing those arguments again, even when the issue of the day should require it. And instinct and behaviour has been repeated time and again, across the board on most subjects.

The consequence of that is that Labour’s analysis of austerity and response to it is winning the debate by default. Similarly, their arguments in favour of much greater state involvement whether in ownership or regulation, are also too often going unchallenged. Ministers and other Tory representatives who should be making the case that individuals, families and other micro-units know best and that a well-regulated competitive market enables suppliers to respond to those preferences, driving standards up and prices down.

One irony of the Labour leadership’s lack of interest in Brexit is that it’s allowed it to concentrate on domestic policy. That might not go down well at the moment with those members desperate to keep the UK in the European Union but once the considerable amount of dust settles from whatever happens over the next few months, politicians will come back to a political consensus that is much removed even from 2015. Arguments that the Tories thought were won in the 1980s and 1990s, and which New Labour accepted and built on have not only been rejoined but are in danger of being lost, not least for lack of practice.

Some might say this doesn’t really matter; that Corbyn is so unpopular and Labour so chaotically managed that they couldn’t win an election. They’d be wrong on two counts. Firstly, the extent of uncertainty in the system at the moment is immense. Labour does have some structural problems but as 2017 showed, they are not necessarily insurmountable. And secondly, even if Labour does lose, public opinion is still being changed by their arguments and any government has to respond to that.

Unless it’s protected better than the current Tory leadership is doing, it could be that one casualty of Brexit is the Thatcher Consensus.

David Herdson