Chris Mason: Faced with an almighty mess PM opts for big shake-up

This reshuffle amounts to the action of a prime minister confronted by an almighty mess - and hurriedly seeking to seize that moment for his own and his government's ends.

This is about as big a reshuffle as you could imagine, short of replacing the chancellor of the exchequer.

Earlier, Downing Street made clear Rachel Reeves wasn't going - a move to calm the markets - but it hinted at the breadth and depth of the reshuffle to come.

"Wide ranging" was how it was described to me by a government insider at lunchtime.

Drip by drip, appointments were fed out through the afternoon.

By teatime, it had met the definition of that word.

Two new occupiers of two of the big offices of state: a new home secretary and a new foreign secretary.

And, for the first time, the three big offices of state below prime minister - home secretary, foreign secretary and chancellor - all occupied by women.

Of course, all of this was prompted by the personal foul-up and foibles of the former deputy prime minister, a nightmarish start to a week Sir Keir Starmer had billed as marking the start of "phase two" of his government, focused on delivery.

Angela Rayner is a big political character, a huge personality in Westminster.

The prime minister could have simply found a replacement for her as deputy prime minister and housing secretary, but instead, he has recast his government in a far bigger way.

Recasting a government is an exercise in authority and jeopardy – and that's just for the prime minister.

For the individuals involved - with ambitions met or punctured - the overlooked, demoted or sacked almost always outnumber the elevated, smiling and promoted.

Hence that jeopardy for Number 10.

Get them right and a reshuffle on this scale can be noticed – and re-energise a government.

Get them wrong or do them too often and a government's progress can become jolty and piecemeal, and the backbench battalion of the disgruntled grows larger.

From the prime minister's perspective, a political battle looms.

After a shaky first year in office, buffeted by shrivelling approval ratings, he confronts a buoyant Reform UK.

Sir Keir has concluded going big was the best option.

He knows he needs to be seen to be delivering and quickly - and he has to hope this new team can do it.