Theresa May is clearly not messing around.

She wants a response from the Russian state to the administration of the nerve agent Novichok by end of play on Tuesday.

If she doesn’t get it or thinks it’s not good enough, she will conclude that this action amounts to an unlawful use of force by the Russian State against the United Kingdom.

This is very serious language. It would mean that the UK held Russia in breach of Article 2(4) of the UN Charter prohibiting the use of force.

It has a warlike air to it.

There has been an element of facetiousness about Russia’s offers of cooperation to date.

Why should Britain ask for the assistance of a state it suspects of a horrendous and brazen attack on British soil which has risked the lives not just of Sergei and Yulia Skripal but of British citizens too?

But full and complete disclosure of Russia’s Novichok programme within what’s now less than 24 hours might be wishful thinking. And then what will Theresa May do?

There is nothing to suggest a conciliatory tone from the Russian side.

Certainly not from the Foreign Ministry whose spokeswoman, Maria Zakharova, has called the Prime Minister’s speech a circus show.

President Putin said earlier today that the British should get to the bottom of this and then we’ll talk.

Well, the time for talking is now.

We don’t know what Theresa May will do when it runs out but she has delivered some tough rhetoric to the British people and she will have to live up to it.

There’s not much talk in Russia yet about a Kremlin response to whatever it is that the British decide to do.

If this was a Kremlin-sanctioned act, then why now – days before a national election, less than 100 days until the World Cup?

What does Russia stand to gain beyond bolstering the electorate’s view that the West is out to get them?

And if it wasn’t, and this horrific poison which the Russian state is known to be capable of producing somehow fell into the hands of those operating without state sanction, then how will Russia ever persuade the UK as much?

Let us hope wise heads prevail on both sides because there are difficult times ahead.
(c) Sky News 2018: May and Putin: What is their next move?