What is this bush/shrub/tree?

If I recall, I found this sprout in the front garden a few years ago & thought what the heck & planted it in the back. A few years on we have a healthy lord only knows what 😂

Google seems to suggest it’s a plum tree; we do have a victoria plum in the front, so perhaps it is & it’s a cultivar? (That the right word?)

Yes, I am aware of the ground elder epidemic. It’s a work in progress!