On one side of the wall are the bright, new, welcoming Olympic façades for Rio 2016. On the other, a drug den guarded by armed traffickers.

As the first of 10,000 athletes start to arrive in Rio on Sunday, they will pass the vivid posters, pasted onto a 10 foot high barrier, stretching for five miles along the motorway out of the international airport.

But the colourful partition hides the inequality that polarises the Olympic city as it prepares to welcome the world.

Behind it lies Maré, a complex of 16 favela communities where life goes on under gang rule except for when under-resourced police carry out increasingly frequent, bloody raids.