In the main press centre, condoms are free – an adventurous innovation even for this, one of the most sensuous cities on earth; yet I found myself paying BRL8 (a bit more than £2) for a croissant. London prices.

On arrival at the international airport, the second poster I saw - after one for Samsung, the International Olympic Committee (IOC) TOP sponsor – was for the Brazilian army, “The force at the Olympic Games”.

This too is an accurate portent of the Rio Olympic experience, with heavily-armed troops stationed at many junctions, their barrels pointed - thankfully - down at the ground.

This still takes me aback even after a week in the city, but none of us is complaining: according to a statistic dating from October 2014 reproduced in the front of my friend Misha Glenny’s outstanding book on the Rocinha favela – Nemesis – “One in every ten people killed around the world is a Brazilian”.

It did not, then, feel too outlandish when I found myself early this morning, after a 45-minute train ride out of the city, walking past a succession of Brazilian army facilities - including one whose emblem appeared to be a snake smoking a pipe - on my way to witness Olympic history being made.

At 11am this morning - August 6 - the first Olympic rugby match in more than 92 years was played at Deodoro Stadium.

Much has changed since the whistle blew for no side in the gold medal match at about 5pm on May 18 in 1924.

Then, in Stade de Colombes in Paris, it was raining; we had blazing sun.

Then it was a men’s match; here rugby’s great Olympic comeback was consummated by women.

Then it was 15-a-side; in Brazil the athletes are playing rugby sevens.

What was constant was the French team.

In 1924, they were favourites to win on home soil against the United States, even though their opponents were the Olympic title holders.

That was not, however, the way things worked out: the implacable US defence was breached only once in front of an expectant 22,000 crowd and the Americans ran out comfortable 17-3 winners, partly, it should be noted, because the home side were eventually reduced to 13 players by injury.

The Official Report for those Paris Games notes that spectators left “a little bit disappointed” at the home team’s clear-cut defeat.

According to Wikipedia, there was a pitch invasion and “the French team, aided by the police, did their best to protect their opponents”. I repeat: did their best to…

The medal ceremony, Wikipedia says, “took place with police protection”.

Such crowd misbehaviour was, it seems, part of the reason why the sport lost its Olympic place prior to the 1928 Olympics in Amsterdam.

But now rugby is back - a fact that makes me feel happy for Bernard Lapasset, the affable, unfailingly courteous Frenchman who piloted its successful campaign for an Olympic return.

I bumped into Lapasset, looking suitably chuffed, just before today’s historic first match.

He is one of the Olympic world’s nice guys and deserves days like today.

Sadly, going by my approximate headcount, there were only around 600 bona fide spectators in the stadium when Spain’s Patricia Garcia, a Madrileña, created that moment of Olympic history by starting the first Olympic rugby match of the 21st century with a precise drop-kick into the French half.

As Garcia later observed, with a nice line in self-deprecating humour, that was "one of the best moments of the game" for her side, who ended up on the wrong end of a 24-7 beating.

Garcia also scored the lone Spanish try. “We didn’t perform our rugby game. We could be better,” she said.

The honour of touching down for the first try of this new Olympic era went to Camille Grassineau - although those relying on the official scoreboard - which accredited the score, I am almost certain, to Marjorie Mayans – would have missed this.

In the mixed zone, Grassineau, a bordelaise, was playing things cool: we’ll see in 10 years if it goes down in history; the important thing was the win, etc etc.

She did say that the dimensions of the pitch were not what they were used to, and indeed the wide open spaces did help the French, whose crisp spin passing was far more accurate than that of their opponents.

The atmosphere did get a lot more lively later, when the hometown Brazilians took the field, especially when, half-way through the first-half, they were on the attack and still level-pegging with their European opponents.

I would estimate that at this point, before Team GB eased to victory, the stadium was perhaps 40 per cent full.

Empty seats are, plainly, going to be an issue for many sports in this the first week of the Games.