This is how my morning went:

I left my apartment at about 9.20am – just before the Olympic women’s Marathon got under way – stopped for coffee and juice at my local bar – and walked the few hundred metres to Botafogo beach.

There, at the 10, 20 and 30-kilometre point in the race, run over three laps, I was delighted to see both that a sharp hairpin bend had been created, meaning the competitors would run directly towards and then directly away from us, and that probably no more than a couple of hundred spectators had gathered.

Those who were there were a colourful and eclectic bunch, including Argentinians, Brits and a couple of especially vocal Bolivians, as well as four Estonians, in blue, black and white, there to support the three Luik sisters, “the trio in Rio”.

There did not appear to be many Brazilians at this point, and the beach football games on the sand beside the course, giving a view of the Pão de Açúcar, were still in full flow.

I took up station beside an Argentinian man, accompanied by his two small daughters, who turned out to be Andrés di Menna, a dirt bike rider and husband of one of the competitors in the race – Maria Peralta.

We didn’t have long to wait: at the 34-minute mark, a couple of motorcycles with headlights glaring in spite of the blazing sun, came into view, then a truck-like conveyance carrying row upon row of photographers, facing backwards, expensive lenses trained on events unfolding behind them, and finally the runners led by Kenya’s Visiline Jepkesho.

The thwock of helicopter rotors overhead competed with the cheers of the good-natured crowd.

The mammoth 157-strong field was already well strung-out by this time; I clocked the last runner, Sarah Attar of Saudi Arabia, as passing us at 44 min 30 secs – around 10 minutes after the leaders.

Argentina’s Peralta too was well down the field, but as she came close we were treated to a wonderful moment as her face lit up and arms stretched out on spotting her family barely two metres away.

Sadly, that was the last we saw of her and the official result confirms that she did not finish.

It is heartening, though, to report that these backmarkers received more applause and louder cheers than the leaders.

By this time, the beach football matches had stopped and local Brazilians were starting to join the crowd. The temperature was up to more than 25 degrees C.

I noticed that a long “Temer Jamas” banner, targeting the country’s Acting President, Michel Temer, who had been booed at the Opening Ceremony, had now been draped over the railings alongside the assorted national flags.

This seemed to be a matter of indifference to the two soldiers in grey camouflage jackets who were patrolling the area.

The 20-kilometre lap went by and I thought little more about it.

Then, as the leading group of six pounded towards us, en route for the 30-kilometre marker, loud shouts blended with the helicopter noise.

I glanced behind me to see a rag-tag group of probably eight or 10, brandishing rectangular red placards reading (in English) “Stop the Coup in Brasil”.

One of the protestors, in a silvery, sequined dress, had a painted clown’s face.

The rest of the field were streaming past by this time and some spectators, mainly Brazilians as far as I could tell, including a man with a push-chair, started counter-chanting and hurling what I assume were insults at the interlopers.

In no time, there was a wholesale slanging match going on in the street of what is a resolutely middle-class neighbourhood.

No violence, happily, and the whole episode cannot have lasted more than five minutes, but it offered yet another window on the tensions that are simmering here at this time of grave political and economic crisis in Brazil.

It is such a contrast from the buoyant picture that pertained in 2009 when Rio was awarded the Games. 

It is cruel and deeply unfair on Brazilians that this global sporting colossus should be visiting when the country has fallen so far from this pedestal.

But that’s the risk that you run with seven-year lead-times: the world might have been stood on its head by the time the circus actually arrives.