Jon Sopel

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We'll get to the G20 in a moment. But let's start with organisational psychology. There are some groups or teams that are greater than the sum of their parts, and there are others - that for all the talent and power they may have individually - are less.

Think soccer. Think last year's European Championship. Then tiny little Iceland were the heroes of the competition - and not just because of their wonderful fans.

This team of part-timers played way above their ranking, there was solidarity, singleness of purpose, real determination. And think of England. Absurdly well paid and pampered players, whose showcase is the Premier League, the wealthiest in the world - and they were just a bunch of inked and primped individuals who seemed to have no team spirit. Dire. Just dire.

And so to the G20. It is not lousy like the England team were - I mean nothing could be as bad as that. But it is less than the sum of its parts.

What of the joint communiqué (that will have been toiled over by bureaucratic draftsmen for days to find a bland enough form of words that all the leaders can sign up to) will be remembered in six months' time? What ringing declaration will change lives? What plan of action will we look back on and think "turning point"?

President Trump has brought to an end weeks of speculation by confirming that he does not have any audio tapes of conversations between him and ex-FBI boss James Comey. So why pretend he did?

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Just before Donald Trump left Washington to come on this gruelling trip, the word was he would have given anything to get out of it or anything to shorten it.

One, he likes his home comforts - not that Air Force One is exactly slumming it - and two, he knew that all his critics were waiting for him to do something gauche or stupid in some faraway foreign clime.

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Before Donald Trump became president he would often spend days holed up in Trump Tower in New York, shuttling in a private elevator between his penthouse apartment and office.

And it's been a similar story since he moved into the White House, where he divides his time between the East and West Wings, leaving only to spend weekends at Trump-branded resorts.

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Washington's big night of pomp and politics - and from the fledgling president a disciplined performance and a well-crafted speech.

From the get-go it was clear this was going to be something different.

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Today totally typified the unexpected and unpredictable nature of covering the 45th president of the United States.

I was at home, working on a book I am trying to finish when there was a flash on the TV: Donald Trump to hold unscheduled news conference in an hour's time.

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As with any resignation there are a thousand small, but nevertheless important questions. Most are of the who-knew-what-and-when variety. But with this astonishing fall from grace there is one big overarching question. I'll save that best bit for last.

The small questions concern whether Donald Trump knew about the calls Mike Flynn was making to the Russian ambassador, and what the substance of their conversations were.

Donald Trump's victory has not only written a new astonishing chapter in American political history, it brings the Obama era to an end in a way few imagined just a year ago.

So how will the first black president be remembered?

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Donald Trump is a hugely effective communicator.

A famous entertainer once said of him he's the best live performer who doesn't sing and doesn't play a musical instrument. He communicates brilliantly clearly.

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"The greatest show on earth" was PT Barnum's claim for his three ring circus.

I'm not sure that is the right description for the 2016 US election campaign, but some variation on that must come close - maybe instead of 'greatest' we could have weirdest, most compelling, unpredictable, disturbing, hate-filled, bizarre.