Cactus in my garden

Cactus in my garden

Observation - Cactus in my garden - Southern Africa. Description: Was given this cactus by someone and never thought it would flower. But now that it has it is very interesting and would love to know what the cactus is called

Was given this cactus by someone and never thought it would flower. But now that it has it is very interesting and would love to know what the cactus is called