Chris Mason: Rishi Sunak's view from the Summit? Trouble back home

International summits are a curious mix of the theatrical, diplomatic and administrative.

Firstly, their scale.

They are a huge undertaking, with massive security.

Little wonder - a collection of world leaders, in the same place, at the same time, at a long-before advertised event.

And so the skies swarm with helicopters and the streets swarm with lanyard-wearing attendees, clutching their all-important accreditation for fear that, without it, even crossing the road might prove impossible.

I spotted two of my colleagues in the travelling British press pack out on a jog the other day, in the driving rain - shorts and T shirts on, yellow G7 lanyards still hanging around their necks.

Pity the poor residents of the host city suddenly unable to take their normal route to work or wherever, because of road closures.

Then there is the theatre.

At the heart of politics are people. Personal relationships matter in politics and diplomacy just as they do in any other walk of life.

And politicians, in particular, have audiences back home to address, images to burnish and impressions to leave.

So there are the theatrical moments, such as Rishi Sunak wearing the red socks - costing £8 we were told - of the Hiroshima Toyo Carp baseball team, whose fans include the host of the summit, the Japanese Prime Minister Fumio Kishida.

This might seem trivial, and is a little theatrical - but it also has a value beyond the pictures.

The relationships international leaders have are so often very brief - one or the other leaves office, and along comes a successor - so acts that help establish and deepen those personal relationships have a real value.

Then, there is the diplomacy.

Winning friends and influencing people? The PM gets a selfie with other world leaders

In the weeks and months before a summit, diplomats for each country discuss their own outlooks and those of others, to try to find common ground.

These diplomats are known as "sherpas" - they lead the way to the summit…

Talking to those who have done just that for the UK, you get a sense of just how much work this is.

The subtleties, the nuances, the different emphases of different countries, on a huge range of issues - and changing all the time.

The political leaders then head to the summit.

In this instance, the PM had been in Iceland the day before setting off for Japan. He got back to Downing Street from Rekjavik at 2am.

The flight to Hiroshima, via Almaty in Kazakhstan, set off from Stansted in Essex at 9am.

We landed in Tokyo at 9am Japanese time the next day, 16 hours later, with a full day ahead.

By the end of the day we had made it to Hiroshima.

When the political leaders come together there is a marathon series of talks, both in big groups, and in one-on-ones known as "bilaterals".

At the end, usually, emerges what is called a communique - the agreed conclusions.

Often broad, often vague, they attempt to take account of every country's position, emphasis and focus on various issues, with the aim being that ongoing discussions can build upon them.

At this summit the communique came early, the day before the end.

There wasn't as much wrangling or even chaos that can occasionally happen.

And then finally, a round of news conferences - an opening statement from leaders, followed by questions, often on a wide range of topics.

I asked the PM about the big political story of the day - the Mail on Sunday and Sunday Times storyabout the home secretary's actions after being caught speeding last year.

He was clearly irritated to be immediately confronted by the conduct of one of his ministers after several long days of international diplomacy.

Little wonder: sleep deprivation, jet lag, complex international deliberations - and then here come (entirely unsurprising) questions about a row back home.

The answer I was given amounted to a holding position: the PM and home secretary hadn't yet spoken about it.

There was no endorsement of Braverman - but no referral to the Independent Adviser on Ministers' Interests either.

Incidentally, we already know Sunak's view on Braverman breaching the ministerial code before he was PM, because he reappointed her as home secretary after she had done just that and resigned.

But it is striking that Downing Street sources are letting it be known that the PM had no idea until the story broke last night about the home secretary's speeding offence, or her request for help from civil servants with its consequences.

He was, I'm told, not informed about it by the Cabinet Office or the Home Office.

No 10 is making it clear that the home secretary hadn't told him, and neither had the Whitehall machine, the civil service.

It is striking too that this story should come via two newspapers, not one, just days after a speech by Braverman that read rather like a future leadership bid.

The story also comes ahead of the publication of new net migration statistics on Thursday.

Numbers are expected to reach a record high, a subject about which Braverman has articulated strong views both publicly and privately within government.

It doesn't appear the government's planned changes to student visas - in particular restrictions on those entitled to bring dependents - will be announced quite yet.

As for summits, there is a Nato one in Lithuania in the summer, and then the G20 in Delhi in September.

What a moment that will be for the PM, and indeed his wife Akshata Murty, were she to choose to accompany her husband once again as she did to Hiroshima.

She was born and grew up in India. He is of Indian heritage himself.