Bugger of a weed - help me get rid!

[ameliarose2012]

I have a weed - the leaves are clover-like, but it grows to about a foot tall, and sometimes sprouts white flowers - that I can't get rid of.

Weedkiller seems to curb, but not kill, it. It grows back as bad as ever.
I spent a week digging it out, and removing as many seeds as possible from the soil. I thought I had it all, but it grew back worse than ever! I know it can grow in the dark (I siphoned off some soil last year and kept it in the outhouse).

I really want to plant some nice plants this year, but it stops anything else from growing . I also want to start a vegetable patch.

Please help me reclaim my flower bed - I'm willing to try anything!

Ooh - oxalis. Had no idea that was a weed. It's growing on a rockery area of our building site garden and is rather pretty, in flower.

It's not necessarily a weed ouryve, but it is to me iyswim. I only have a small garden, with a small flower bed, and it has taken over!