Beginner Gardening: Large Cactus, 2 by Crispy500

Crispy500 wrote:
I have 4 or 5 very large cacti in my garden, that have grown rigorously over a few years. (See pictures, but not the Yuccas! - The very large leafed (and painful) one that now has an enormous central stalk growing out of it!) The stalk is the bit with slightly reddening leaves) and it has now reached around 9 feet tall!

My question(s) are - What is the name of the cactus, and what is the very tall stalk? Does it flower, or is it more leaves.

All help and advice welcomed