When I was working for Ben Brogan at the Telegraph, he always used to tell me of the importance of "stress-testing the narrative".

Donald Trump's decision to authorise missile strikes on Bashar Al-Assad's regime in Syria - the first direct intervention by the United States in the Syrian war - upends many of our assumptions about America's new president, but confirms others.

Yes, the investigation into whether the Kremlin may have co-ordinated with the Trump campaign remains open, and Trump may well owe his presidency to Russian interference. But it's hard now to claim that the Trump administration is a puppet of Vladimir Putin, particularly as Rex Tillerson has separately announced that it is now the American government's objective to seek "regime change" in Syria.

As far as the need for a response to Assad's use of sarin gas goes, it's worth revisiting Rory Stewart's 2013 blog. His case for the importance of a response (that the international prohibition on the use of chemical warfare should remain in place) remains convincing while his three conditions that response must satisfy (not to make the conditions for the civilian population worse, to deter Assad from using chemical weapons again, and to send a clear message that the use of weapons will not be tolerated elsewhere) continue to be essential. And as Yvette Cooper noted in her excellent 2015 speech, there can be no defeat of the self-styled Islamic State that doesn't involve the permanent removal of the Assad regime as well.

(It's worth noting too that the attack has been welcomed by the bulk of Syrian activists.)

There's a "but" coming though, and it's a big one. All of that has be weighed against the parts of the Trump narrative that have been reinforced, and terrifyingly so, by last night's bombing. The first is that Trump has acted without Congressional or international authorisation, part of the pattern noted in this week's Spectator: that Trump's approach is war and more war, and largely without legislative oversight.

The second is what it confirms about the volatility and unreliability of Trump. The case against "narrowing the circle of what is prohibited" as Stewart put it remains unchanged since 2013 when Trump angrily campaigned against bombing. The case against Assad as part of the solution in Syria remains unchanged since last year's presidential race, when Trump ran on a platform of doing a deal with Assad. When the facts change, I change my mind: but the facts haven't changed. What has changed is that Trump saw something he didn't like on TV. What will he see next week?

That Trump has acted against the use of chemical weapons and in accordance with the wishes the bulk of Syrian activist groups should be welcomed. That he has done so without authorisation, apparently off the back of a TV report is worrying.

As I wrote earlier this week, the absence of direct intervention in Syria has been a disaster. That doesn't mean that the unauthorised and inconsistent intervention of a volatile president will be any more successful.