This is an unpacified favela, one where criminal gangs still hold sway. And Caton and his team of volunteer, largely expat Antipodean coaches have been escorted by a cohort of heavily armed police to the dust-bowl pitch where they are conducting their session.
At first glance, it is hard to see why the cops are needed, given the only people in evidence are gaggles of noisy youngsters. The lawmen stand around the fringes of the pitch paying the action no attention, staring at their smartphones, their automatic weapons holstered. But the coaches have been warned that word of outsiders can quickly spread, attracting those who would use whatever means necessary to relieve them of their valuables. Not to mention the bag of rugby balls they have brought with them.
It may be risky, but this is partly the purpose of the programme. Not simply to raise awareness of the game in a land with no history of engagement with an oval ball, but to take it into places starved of sporting investment and infrastructure. And there to pass on the values integral to the game: discipline, respect, sportsmanship. Plus, the British Council hopes, some of the traditions of the country that invented it.
Although it is no more than a couple of miles from Rio's glorious beachfront, most of the children throwing the ball around have never left this favela in their brief lives. The only way to introduce them to the sport is to take it to them.
"We host taster sessions on the beach here every week," Wayne Morris, Premiership Rugby's director of community, says. "But for these kids, that might as well be on Mars."
Try Rugby has been running in Sao Paulo for two years. More than 14,000 play every week there - 38 per cent of them female - which has doubled the rugby playing base in Brazil. The hope is that the move into Rio will double that number again.
"This sport is not going to come to an end in this country in 2016," Morris says. "That is just the beginning."
There are, inevitably, initial problems. "Most of them think it's American football," Juliet Short, an Irish international who has been coaching in Sao Paulo since January, says. "All the boys initially throw the ball like quarterbacks. I'm shouting 'no Americano' all the time."
Though, she adds, language is not an issue. "If you're really animated, it's like a cartoon picture, if something's really bright and loud it's easy to understand, people are mesmerised. If you're confident, people believe in it."
There are certainly aspects of the game the youngsters are quick to adapt, however steeped in football they might be.
"You have girls who know about soccer and the merest brush on the shoulder or tap on the ankle and they're down, rolling around," Short says. "It's like, 'aaagh'. I have to say, 'no fraca', no weakness. And they're like, 'okay'. So now, they shrug it off and carry on."
Brazil will enter teams in both the men's and women's sevens competition next summer.
The men are unlikely to be anything other than cannon fodder. But the women, 10 times South American champions, could make a huge impression on the country if they come close to the podium. Not that most of the children in the favela are even aware rugby is in the Games.
Just as if you had asked a group of primary school pupils in Hackney ahead of London 2012 if they knew about handball, the Brazilian youngsters are blankly indifferent. Get them involved in a game, however, and they love throwing and catching and running with the ball.
Indeed, later, on Ipanima beach, watching a game organised by the Try Rugby coaches, it is quickly evident that sevens rugby is a sport ideally suited to local conditions. With the ball in hand, the group of locals and expats move across the sand with speed and grace, drawing a crowd of impressed onlookers.
It works much better than beach football, for the simple reason the ball is not slowed by the sand all the time.
There is a real sense that this could catch on. And, the 21st-century sporting equivalent of the 19th century missionary, Short, for one, is convinced it will.
"I feel really blessed I can share my passion for the sport," she says. "Share what it means for me. Rugby has saved me, helped me with respect and solidarity, I really believe in the values.
"For me to share my love is a once-in-a-lifetime opportunity."
- Telegraph Group Ltd