Image copyright Getty Images

They call it Rolling Thunder. And with good reason. At six this morning from my bedroom window I could make out a low level rumble in the city that you never normally hear.

It was the sound of a million or so bikers - a large number of them from the Vietnam era - converging on the Pentagon car park ahead of their rally around the city's most iconic landmarks.

It's to remember those held prisoner of war, and those who went missing in action and whose bodies have never been recovered.

On their leather vests are the badges that read like a history of US military engagement over the past 50 years - Vietnam airborne division, Desert Storm artillery, Operation Iraqi Freedom, Afghanistan and the list goes on.

One veteran told me he had worked with the British SAS at the time of the Falklands War in 1982.

They make the pilgrimage from all over the US to be in Washington to visit the memorials on Memorial weekend.

Media playback is unsupported on your device Media caption Jon Sopel explains why Donald Trump wants biker vote

It's hard to do solemnity when you have the deep, basso throb of the combined orchestra of thousands of 1700cc v-twin Harley Davidson engines - but somehow these former vets pull it off. Though not all of it is entirely biblical.

Just before we leave the muster point at the Pentagon, a speaker comes to life urging silence for the presentation of Colours and the singing of the national anthem. All done with due decorum.

Then we are told there will be a prayer. The prayer starts uncontroversially enough as we all stand, across this vast parking lot, heads bowed, right hand across the chest.

But then I think the preacher veers a little bit off course, with some strong language, as he says: "And if you wish harm upon this country then you are a son of a bitch, and may you burn in hell."

I am not an expert on the King James edition (new or old) of the Bible, nor the New American Standard Bible, but I'm sure that phrase didn't make the edit.

Image copyright Getty Images Image caption Spectators interacted with the riders

That done, it is time to saddle up and make our way out into the city. Around 40 police outriders lead the parade.

We drive out, Arlington military cemetery to our left, and then over the memorial bridge that crosses the Potomac, with the Lincoln Memorial on our right.

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Huge crowds are lining the streets. People are waving and saluting the vets. Some seem overcome by emotion and are tearful as they wave at some of the old boys on their Harleys.

I feel a total fraud to be riding near the front of the parade (on a British bike as seems befitting for someone representing the BBC!), but it is hard not to be swept up in the occasion.

Image caption Jon Sopel prepares for an emotional ride

Amidst the emotion of remembering those comrades who didn't come home, and admiring the extraordinary artwork and shiny chrome on these incredible bikes (you can't separate the veterans from their bikes, if you see what I mean) there is also politics.

And because this is an election year, it is politics with a capital P. And heading the bill at the post-ride rally was Donald J Trump.

I spoke to a large number of the bikers before we set out on the ride. And something struck me - yes, there were Trump diehards who think he will prove to be the saviour of a fallen nation that has lost its way.

Image copyright Getty Images Image caption There were plenty of Trump supporters - and Clinton haters

Image copyright Getty Images

But many others were much more nuanced. Many people said to us that he would be the lesser of two evils, the clear implication being that Hillary Clinton was the bigger evil.

One person, when I asked what he thought of Secretary Clinton, said: "She's trash, she should be in prison."

Another man told me that his views were simply unbroadcastable on television.

The polls say that both Trump and Clinton suffer big negatives and low approval ratings.

This election might come down to a question of who voters loathe the least.

My totally unscientific, random, non-adjusted focus group at Rolling Thunder suggests that might well be the case.

In a country of 320 million people, how did it come down to such an unappetising menu choice?

Do you want the dish with the listeria or the salmonella?