Cleistocactus

C. straussii, to be exact. Lovely tubular scarlet flowers once it exceeds 70 cm. It's pollinated by hummingbirds in its native habitat.

Thanks for the information. It's about 7cm at the moment so I've got a bit of a wait, lol.

It's fairly fast for a cactus: around 30 cm per year in good conditions, slower in a small pot.

It's in a tiny pot but I won't pot it on until the spring.

Yep, I can't imagine them growing much in an English winter, even in a greenhouse! : )