It might not have attracted as much attention as the departures of Dominic Cummings and Oliver Lewis, but Downing Street is losing another of its fighters. Nikki da Costa, the pugilistic Director of Legislative Affairs, is expected to leave Downing Street in October.

Some in government are worried that the legislative affairs function may be sidelined or downgraded before da Costa’s successor is confirmed. They point to the line of thought expressed by one Number 10 source quoted in above: “The PM will continue to receive advice on parliament from his Chief Whip and Leader of the House of Commons.”

At first glance, this might seem reasonable enough. It’s one thing to need a legislative strategist when facing the extraordinary circumstances of the last Parliament, after all. But is it really necessary when the Government enjoys an 80-seat majority?

However, there are several reasons that the Prime Minister should be cautious before he allows Legislative Affairs to go the way of the Union Unit.

Parliamentary management is still important

Reports that the Government is going ahead with ‘Freedom Day’, in part because it doesn’t have the Conservative votes to prolong restrictions, are just the latest evidence that parliamentary management remains a more fraught process than it might have been for a government with a similar majority in decades past.

The habits acquired in the previous Parliament haven’t just been un-learned. MPs are now organised into more backbench groups than ever before. They have learned new tactics, including better collaboration with like-minded members of the House of Lords.

Boris Johnson must also consider the political reality that whilst his Government may be fairly fresh, the Conservatives have held office since 2010 and the main thing he was elected to do has, however imperfectly, been done. He’s also had plenty of time to promote the people he’s going to promote, and for the people he isn’t going to promote to notice.

For better or worse, this group of Conservative MPs are likely to be much more transactional in their loyalties than those typically found supporting majority governments barely 18 months into office, and will thus require more careful handling – especially when the Government has a packed legislative programme including some extremely controversial Bills.

(All this is compounded by the recent departure of Roy Stone, who served as the Principal Private Secretary to the Government Chief Whip since 2000 – a serious loss of institutional knowledge.)

The Chief Whip and the Leader of the House have different functions

Can the Prime Minister not, as the papers suggest, fall back on Mark Spencer and Jacob Rees-Mogg? After all, it is the former’s business to know what MPs are thinking and the latter’s to make sure the Government gets its legislative agenda through the House.

Such proposals might cheer traditionalists who dislike the expansion of the Downing Street operation under successive governments. But they must address the fact that it would actually be quite difficult for either Rees-Mogg or Spencer to simply fill the gap left by a weaker legislation unit. The Leader’s office is focused on the mechanics of getting the Government’s programme through the House. The whips are responsible for tactics and triage, defending Government business as it progresses through Parliament.

Neither of them are strategic in the same way the Number 10 legislative operation is. Nor can either systematically feed into the process inside Downing Street.

A system that rested on the Leader’s Office and the Chief Whip alone would thus almost certainly – through no fault on the part of either man – be more reactive than the one which ‘got Brexit done’.

There are plenty who might think that’s a good thing, probably including the judges who overturned Johnson’s prorogation. But with an ambitious legislative agenda to deliver, the Prime Minister should take care to ensure his parliamentary operation is as effective as possible.