Why Donald Trump may have waited until today to sack Mike Waltz

Timing's everything for Donald Trump.   The time for sacking Mike Waltz was, clearly, not before the 100-day milestone - the measure of his performance in office.

The national security adviser had his card marked from the day the 'Signalgate' scandal broke. Trump latest: Waltz 'leaving White House' hours after TV appearance In any other government, at any other time, political expediency would have demanded his immediate sacking.

To have shared sensitive military information on a group chat is a most reckless error of judgement. Bad enough that the information reached the inbox of a US journalist - who knows who else might have accessed the information in what is a commercially available app? China, Russia? Iran, the very country that backs the Houthi rebels who were under attack? Initially, Donald Trump defended Waltz as a "good man" who had "learned a lesson".

The president will have known, though, that he's a man who has fundamentally weakened him. Waltz's mistake put the lives of US service personnel at risk and called into question the credibility of his ultimate boss.

The emoji-laden group chat read like the stuff of excited youngsters breathlessly sharing gossip. It was recklessness over responsibility at the heart of government, and it reflected on the commander-in-chief and his judgement in appointing Waltz in the first place.

To keep him in post for weeks following the scandal looked like an acceptance, of sorts, and it didn't look good. If there are questions about the circumstances surrounding Waltz, there are, too, about Trump's defence secretary, Pete Hegseth.

Hegseth was also part of the Signalgate group chat and more. Separately, he shared messages on Signal with his wife and brother about military strikes.

Both are involved with the Pentagon, but are nowhere near the security clearance typically required to access that kind of detail. Read more from Sky News:Musk fury over report Tesla looking for new bossHarris attacks Trump in biggest speech since election If Waltz committed a sackable offence, why didn't Hegseth? It's a question that won't go away.

The answer, I suspect, is that Donald Trump invested considerable political capital in forcing Hegseth into position, in spite of strong opposition. In a story that acknowledges weakness at the heart of government, Donald Trump has his limits..