The infamous Oxalis cornuta. It is now recognised as one of the most invasive of species worldwide.
Sadly the only way to even control it is vigilance and Glysophate (Roundup). It seeds everywhere and the roots are covered in minuscule 'bulbs' which brak off and grow again.
In my gravel areas I use the Flame Gun on them to at least burn off the seeds.
Sorry to be the bearer of bad tidings.

O
It needs to be said, sometimes, and you were brave enough to step up!

A lot of nurseries are infested with it and it then spreads to your garden.

It even survives the processes by which they make the non-peat compost too!

You'll never believe this, but the first time I saw it i thought how pretty it was and dug a bit up for my own garden. It has been with me ever since, through two house moves.