As reshuffles go, it was more akin to rearranging the deckchairs on the Titanic than the night of the long knives.

Keir Starmer has appointed new leaders at no fewer than 10 departments as he attempts to realign his government once more after an underwhelming first year. However, only one appointee is new to the Cabinet; there’s little infusion of fresh faces, with the hope resting on Sir Keir’s close associates performing slightly better in their new roles than they did previously.

The scale of the reshuffle was prompted by Angela Rayner’s unexpected resignation and the desire among some in No 10 to gracefully transition Yvette Cooper out of the Home Office, with the aim that Shabana Mahmood’s assertive approach can more effectively address the issue of illegal immigration.

It also underscores an apprehension about relegating influential adversaries to the backbenches. It’s far more straightforward to reassign underperforming ministers than to confront and remove those who fail to leave a mark.

The PM is right to be worried, because politics is about to get much tougher for him.

 Newly appointed Justice Secretary and Deputy Prime Minister, David Lammy, arrives at Number 10 at Downing Street amid a dramatic reshuffle

Yvette Cooper has been moved from the Home Office after Labour’s failure to tackle the small boats crisis

Shabana Mahmood is replacing Yvette Cooper as Home Secretary as the PM battles to get to grips with the migration crisis threatening his government

Sir Keir and Angela Rayner have had their share of disagreements over the years, even leading him to attempt to dismiss her at one point when she seemed to be overshadowing him.

However, her media-driven resignation delivers a significant setback to a leader who this week initiated ‘phase two’ of his administration in an effort to overcome the setbacks of ‘phase one.’

Sir Keir and Labour’s ‘Red Queen’ were contrasting characters. Yet, over time, the reserved bureaucrat grew to depend on his dynamic, emotive deputy.

Since entering government, Ms Rayner has performed a critical role in keeping a lid on the Left of the party, which has struggled to adjust to the realities of power.

Labour MPs credit her with several interventions that headed off catastrophic errors in Labour’s first year – most notably when she brokered a climbdown over welfare cuts to prevent the government suffering a humiliating Commons defeat.

Her political instincts are much surer than those of the Prime Minister. Or, as one Labour MP put it: ‘She’s the one who really gets our people; she’s the one who really connects with them.’

Tears: Angela Rayner admitted failing to pay thousands of pounds in stamp duty and an inquiry found she should have taken proper tax advice

Health secretary Wes Streeting had seen Ms Rayner as a future leadership rival

Her dramatic departure forced Sir Keir to bring forward a reshuffle that had been repeatedly put off.

But it will also trigger a contest for the elected position of Labour’s deputy leader, which looks certain to lay bare Labour’s growing divisions.

The winner looks unlikely to get the title of deputy PM, which was handed to David Lammy as a consolation for losing the Foreign Office.

But there is every chance now that Labour members will use the contest to shift the government further to the Left. All the internal debates over wealth taxes, public ownership, immigration and Gaza will now be fought out in public. And the winner – who is quite likely to be further to the Left of Ms Rayner – will have their own, fresh mandate to deliver in government.

Then there is the question of what she will do next. Ms Rayner was the most popular Cabinet figure with Labour members bar Ed Miliband – and the clear favourite to one day succeed Sir Keir.

If she chooses to, she could now become a powerful figure on the backbenches pushing for a change in direction, dragging Labour further back into its Left-wing comfort zone.

Even if she does not, Sir Keir now faces a destabilising period in which potential future leaders such as Wes Streeting, Andy Burnham and Bridget Phillipson jockey for position.

In the end, the report into Ms Rayner’s conduct was black and white, finding that she ignored advice to seek a specialist opinion on how much tax she should pay on a luxury £800,000 apartment in Hove.

Sir Keir had no choice but to sack her. But her departure means that a government that lacks a clear vision for the country has now lost one of the few members who had an instinctive feel for what Labour should do.

And it opens up a new period of instability for Sir Keir just as he was trying to assert his grip after a dismal first year.

No wonder, the PM went out of his way to try and save her.