Identification of Granddad's Mammilaria

I inherited the Mammilaria below from my Granddad 31 years ago. I was thrilled when it flowered for the first time this June, and I am now wondering what species I inherited.  It might have flowered because this year I have given it a summer holiday in the greenhouse (it normally resides indoors).

Please can anybody identify it? I am only a novice cactus owner so am unsure how to do so.

Many thanks.

This could be an echinopsis (or related to that), but it certainly isn't a mammillaria.
However, the white spined plant in the back is a mammillaria. Possibly M. geminispina, but it needs a lot more light. And I think that the echinopsis also would welcome more light.

Wolter ten Hoeve.

Thank you Wolter. As you can see I am a novice.

Anybody any ideas which Echinopsis?

Many thanks.

Its possibly Echinopsis huasha or a hybrid involving that species. The narrower growth indicates a period of too little light which probably also led to the dark markings on the stem, but that galsshouse looks nice and bright and the new growth is much healthier, now rewarding you with a flower Both this one and the Mammillaria will appreciate the brightest spot available.