Perhaps Vladimir Putin now feels Russia is so strong and Britain so weak that he can break the unwritten rules of espionage – and seek to murder a former spy, and his daughter, on our streets.  Or maybe the operation was unauthorised.  Or it could be that Sergei Skripal hadn’t retired after all, and Putin wanted to send a very public message to the security services, and to others, that Russia won’t tolerate such manoeuvres.  Or it is possible that there is some more exotic explanation.

Any Tinker Tailor Soldier Putin yarn makes irresistible copy and spawns frantic guesswork.  But a less startling though ultimately more significant event should help frame the way we think about Russia.

Last month, Gavin Williamson told the Defence Select Committee that it has ousted terrorism from the top of the national threat list.  In 2015, the National Security Strategy put the terror threat first, and framed the country as a possible partner (“notwithstanding our differences, we will seek ways of cooperating and engaging with Russia on a range of global security issues, such as the threat from ISIL”), as well as a potential threat (“we cannot rule out the possibility that it may feel tempted to act aggressively against NATO Allies”). In the 2010 strategy, state-based threats to our security were only vaguely referenced: “the emergence of old or new regional powers” was listed alongside state failure, competition for energy and the destabilisation of the Middle East by “a nuclear-capable or nuclear armed Iran”.  Russia wasn’t even named.

As Mark Francois, the former Defence Minister, suggested at the select committee session, and as the Defence Secretary confirmed, this changed Government analysis has spending implications – and backs up the latter’s drive for more cash.

Defence and health are now the two main spending pressure points on the Chancellor.  And it so happens that were the proportion of our GDP to rise to three per cent of GDP, or that fabled £350 million a week to go to the NHS, then roughly the same extra sum would be spent in each case – £18 billion or so.  The good news is that, largely due to the work of the Coalition, Britain is at last in surplus.  The mills of George Osborne ground slowly, but they ground exceeding small.

It doesn’t follow, of course, that Philip Hammond is in a position simply to roll over, and give the big spending departments anything they want.  But he should certainly meet Williamson more than halfway.  We don’t need attempted murder in Salisbury to tell us that.