This was a true giant i met in Rio de Janeiro town, amazing really!

Maybe Furcraea selloa var. marginata.

https://images.search.yahoo.co...

That really looks like the right genus Dave!
But maybe Furcraea foetida (the variegated one in this case) is more likely as it is native to Brazil..
https://www.google.be/search?q...

it has as a synonym Furcraea gigantea, very appropriate for its size!
http://floradobrasil.jbrj.gov....

I'm pretty sure it's Furcraea selloa as it has toothed margins. I used to grow the plant. <I>Furcraea foetida has entire leaf margins and the mediopicta cultivar is variegated on the inside of the leaf, rather then on the margins.

You have convinced me!