As the lights went up on the carnival parade, Sidney started to get hot around the collar of his new "Rio - I'm here to party" T-shirt.
"Quick," he said to his younger brother, Charles, "pass me that hankie, will ya. I'm feeling the heat."
"Not surprised", retorted Charles. "You've had too much sun. I mean, will you look at the colour of your head."
"No, it's not the sun, stupid. It's . . ." He paused and started pointing his finger excitedly, ". . . it's that."
The two Yorkshire men, both in their 70s, leaned over the rails of the concrete sambadrome terrace and stared.
Wrapped in a rainbow of feathers, a young blond woman was strutting below them, wearing nothing but an elaborate headdress and a sequinned G-string.
She was covered from head to toe in gold body make-up, which made her massive silicon-enhanced breasts glisten in the floodlights.
"Quick! Give me the cam corder," said Sidney, zooming in on her impossibly huge bust.
Breasts have been big news in Rio of late. And this year's carnival, dedicated to retelling the 500-year history of Brazil, was no exception.
In January, after police arrested a topless bather for contravening obscenity laws, the country went mad with indignation. Dozens of women, protesting at the heavy-handed police action, engaged in topless protests on the city's golden sands.
Brazil's weekly news magazines devoted pages to the controversial issue, arguing that a law should be passed allowing women to sunbathe as they pleased.
With the clamour mounting, the state's legislators decided that the original bather should be released without charge, and condoned future topless beach activity.
Sidney and Charles knew none of this. Nor did they know that the 14 samba schools that make up carnival were exposing more breasts than ever before. Full of spectacle, the floats depicted everything from exotic jungle beasts to the torture victims of the military dictatorship. And as this fantasy parade filed past Sector Nine, the crowd went wild with excitement.
An American woman, who looked like Ruby Wax's older sister, started dancing. Grinding her pelvis in time to the samba beat she looked through her expensive binoculars at the explosion of jiving colours below.
Six middle-aged German men, wearing sandals with socks and identical red T-shirts bearing the legend "Are you pissed yet?" swayed from side to side, out of time with the music. Whether this was the effect of the beer they were packing away or the sight of so much naked flesh was unclear.
When the school's parade finished 90 minutes later, the crowd in Sector Nine sat down. Getting out his flask, Sidney had a cup of tea and a digestive.
Cleaners, dressed in orange uniforms and blue baseball caps, started to sweep up the debris - the confetti, streamers, loose feathers and sequins - ready for the next school's parade.
Suddenly one of the cleaners, a young black guy in his 20s, put down his broom and started to samba to the background beat. The crowd roared, giving him the biggest cheer of the night.
Encouraged, he picked up his broom and held it close to him as though it were his dancing partner and spun his way down the entire 700-metre length of the sambadrome parade ground, enjoying his few moments of fame.
Chris found this display particularly amusing. The accountant from Berkshire was, he said somewhat shyly, having a very good evening indeed.
Dressed in a white vest, which was just a little too tight for his business-lunch belly, Chris introduced his partner, Luciana, a Brazilian woman in her mid-20s.
He refused to say when or how they had met and insisted on repeating: "I am very, very happy."
With the Sector Nine crowd seated awaiting the next samba school, Luciana decided to give the assembled spectators a show of her own. She stood up and started wiggling, first her chest and then her behind.
Round and round she went, thrusting her pelvis at Chris and planting big lipstick kisses on his grey stubble face.
Chris decided to join in the fun. He got up and started to shuffle awkwardly in time to Luciana's rhythm.
"Now will you look at that?" said Sidney, pointing at Luciana's wobbling behind. "Well, I never. Pass me that video recorder again, will ya."