The massive scramble behind the scenes before the new PM arrives

Welcome to limbo land. Unless a meteorite crashes to earth, Scotland wins the World Cup after all, or the ravens leave the Tower, in just over a fortnight, Andy Burnham will walk up Downing Street as the 59th British prime minister.

We are, once again, in a bizarre in-between political moment. An informal transition where the man technically in power has no authority. But the man with all the authority doesn’t yet have any real power.

What, though, is actually happening while the Starmers get ready to pack their bags, and the Burnhams prepare for the day that will change their lives?

This afternoon, Burnham is taking a break, watching his rugby league team, Leigh Leopards, take on the Warrington Warriors. And tomorrow night he’ll stay up with his family to watch England play Mexico.

But that’s only a brief respite. In public, every move he makes is being pored over to an incredible degree.

The next prime minister hasn’t fought a general election, so hasn’t published a clear manifesto, meaning Westminster’s hungry for clues.

Since becoming an MP again, he’s only made one big speech, given one radio interview, and taken questions from the public on social media.

Using Reddit or Instagram does make politicians more accessible to the public, allowing you, not journalists like me, to push them. Remember, though, it also gives them the power to pick and choose the topics, or the questions they want to answer.

So right now in government, officials are “rushing around picking up every little hint and tidbit on areas that might affect their department”, in the words of one former senior figure.

As we talked about last week, Burnham’s broad approach to politics has been clear for years. In his speech last Monday, he gave some details of what that would mean in practice, with a “No 10 North” in Manchester, where he wants to spend some of the week.

On Thursday, he repeated his plan to give a tax cut to pubs, and small independent leisure and retail companies, paid for by levies on giant warehouses operated by big online firms like Amazon.

Burnham has indicated he will broadly stick to the Labour manifesto from 2024, but says it has “room for manoeuvre” when it comes to tax, for example.

He also wants to expand public control of utilities, some of which is underway already. Every nudge he gives is seized on in public, and in Whitehall’s corridors of power.

Beyond the limited amount the likely next prime minister is saying in public, this limbo period is frantic behind the scenes politically and practically.

Burnham spent the week in meetings with MPs, and a crunch session with the powerful unions. And there’s a talent contest going on inside the Labour Party, with Andy Burnham the Simon Cowell, and aspirant ministers auditioning for their place.

It’s what one MP describes – in colourful language – as the “greatest show of arselickmanship you have ever seen”, telling me, “there’s a bunfight for jobs, a bunfight for Cabinet and a bunfight for political space”.

But the man himself is not expected to announce his team until he’s almost through the black shiny No 10 door.

He’s told colleagues he’ll set the direction of his plans before deciding who gets what job. The wannabes will have to wait. Burnham, for now, holds all the cards.

But even though he is not yet the Labour leader, a formal handover process has begun – “access talks”.

Just like before a general election, the incoming team has been given permission by the sitting prime minister to start conversations with the civil service about what they want to do.

Cabinet Secretary Antonia Romeo, the country’s top official, is running the process and Burnham himself has led the talks.

Alongside him have been his chief of staff (former cabinet minister and old flatmate James Purnell) and Lou Haigh, the MP who has been critical to his campaign and served in Starmer’s cabinet.

The focus so far as been on devolution, the grisly state of the country’s books and the security threats the UK faces. And there’ll be more talks in the coming week.

For all the vital high-level talk about plans and policy, there are also the basic practicalities of the preparation for the big move-in day, when everything official changes.

One former No 10 staffer recalls arriving early in the morning, being “shuffled through weird corridors, taken into a room, choosing logins and signing our lives away”.

How will Team Burnham choreograph the moment where he walks up to the lectern to address the country?

Keir Starmer’s team agonised over whether to bring crowds of supporters into Downing Street to wave and cheer his arrival, worried “it would look too gauche to have a celebration”.

But in the end, they did plump for an image they hoped would be “strong and patriotic”, according to one of them, with Union Jack brollies on hand in case it poured, and supporters waving flags.

It will be Burnham’s first official introduction to the country as prime minister, an image that will be seen by millions, and a speech that will be quoted again and again.

Inside the building, permanent civil service staff will be conscious they are saying goodbye to one team as well as welcoming another. And that’s not always straightforward.

One former official recalls a departing prime minister being peeved there was an “office spruce-up”, with walls being freshly painted for their replacement about to arrive.

New prime ministers, like the monarch perhaps, maybe get used to the smell. The renovation of the men’s loos outside Theresa May’s office into a more pleasant waiting area for her guests had only just been finished when her time was up.

Officials stop copying departing political staff into important emails as power drains away.

I’m told there is epic desk tidying to make a good impression when the new boss arrives. And on the day itself, a frantic rush, as one leader will be clapped out, and less than two hours later, a new one clapped in.

And on that day, it’s a strange combination of the deadly serious and the banal – from a heavy security briefing, to what kind of desk the prime minister would like, and where he wants to sit. There will suddenly be hundreds of decisions, big and small, for the country’s new leader, and his new chief of staff.

“James Purnell will be weirdly dragged into having to worry about the toilet paper as well as when he is going to write his letters to the nuclear submarine commander,” a former official jokes.

One of the most sombre tasks every new prime minister carries out more or less immediately is writing four of those letters, to the commanders of Britain’s four nuclear submarines – the letters of “last resort” – with instructions on what to do in the eventuality that the UK government has been destroyed by a nuclear attack.

From the gravest to the most basic, a set of choices will confront Andy Burnham as soon as he walks through the Downing Street door.

Remember he’d hoped to have longer to get ready. Key allies had hoped Keir Starmer would stay on until September, and give them time to prepare.

But while he looks near certain to achieve his biggest goal, finally becoming Labour leader (which he first tried in 2010) and then prime minister, the hope of a couple of months to get ready was dashed.

An ambition more than 15 years in the making. Only 15 days to go.

To picture credit: Getty Images/ EPA/Shutterstock

BBC InDepth is the home on the website and app for the best analysis, with fresh perspectives that challenge assumptions and deep reporting on the biggest issues of the day. Emma Barnett and John Simpson bring their pick of the most thought-provoking deep reads and analysis, every Saturday. Sign up for the newsletter here