Sky News crew set off for 18-hour journey across North Korea to nuclear test facility

We are finally on our way to the nuclear weapons test site at Punggye-ri after being delayed for one night.

The wait could either have been because of the weather - as our North Korean minder has told us - or because of how the winds are blowing over in Washington, where South Korean president Moon Jae-in is meeting Donald Trump.

So we sat and waited in the Kalma Hotel in Wonsan, where dinner includes "lion-shaped meatballs" and "smothered orange crepes" and will set you back $50 (£37) - our North Korean hosts are certainly keen to monetise our presence.

On Wednesday afternoon the eight South Korean journalists who had been refused entry the day before suddenly arrived and we were given an hour's notice that we would at last be leaving for the test site.

We now have an 18-hour journey - 12 hours on a train, four on a bus and a two-hour hike.

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And we're wondering: How much importance should we attach to the closing of the Punggye-ri test site? And to the fact that we've been allowed to watch it?

First, it's worth noting how unique Punggye-ri is. It is the only active nuclear weapons test site in the world. It's where the North Korean regime has detonated six nuclear devices, the most recent, in September, a massive hydrogen bomb. To let foreign reporters in to see a place like that is extraordinary.

But this is where the objections mount. Kim Jong Un is welcoming reporters, not weapons inspectors, who might be able to more comprehensively verify the regime's claims. And even us journalists have had our dosimeters confiscated so we can't independently confirm how much radiation (if any) is leaking out of the site.

Then there's the site itself. Some reports have suggested that it's now unusable thanks to a tunnel collapse, triggered by detonation after detonation. Six nuclear blasts is a lot even for a mountain to endure.

And the final argument - Mr Kim has already proved, to his and the world's satisfaction, that he has a nuclear weapon of terrifying power. He simply doesn't need to do any more tests, so shutting down Punngye-ri doesn't mean all that much.

Those points are good ones, although you can deal with them one by one.

In reverse order: The last test might have been impressive but the North's nuclear programme is far from complete - not least in demonstrating the ability to fit a warhead to a missile that successfully reaches its targets.

That would require further testing. At the moment, neither the West nor Kim himself really knows whether North Korea could do this reliably and accurately. But the chance isn't worth taking.

Second, even if Punggye-ri is out of action, there are plenty of mountains in North Korea. It would be easy enough for a totalitarian dictatorship to build another test facility.

Third, if Kim is promising not to conduct any more nuclear tests - well, you don't need weapons inspectors to check that. They show up as glaring seismic events continents away.

The decommissioning of Punggye-ri is therefore total symbolism. That's why camera crews are here, not weapons inspectors. But that symbolism is hugely important.

Kim has pledged no more tests - an easily verifiable claim. If he reneges on that, he makes a very public, deliberate choice - the opposite of hiding a weapons program in secret.

More importantly, the path to peace is paved with photo ops.

The rapid turnaround in the situation on the Korean peninsula has been captured in three moments full of imagery and symbolism.

The North Korean delegation to the Winter Olympics; the meeting of Kim Jong Un and Moon Jae-in in the demilitarised zone between their two countries, still technically at war; the handover of three American political prisoners to the US, shown off by a deliriously happy Donald Trump at Joint Base Andrews in Washington. All photo opportunities.

But photo ops that have pushed things closer to peace, stunts that have built momentum when the difficulty of complex geopolitical negotiations have slowed it.

And every one of them crafted not by that arch TV manipulator Donald Trump, but by Kim Jong Un. His father and his grandfather understood the power of image to buttress their authoritarian rule at home. Kim understands how to deploy it abroad.

And that's why, even if Punggye-ri is a photo op, it matters. A lot.