Help identifying a plant/identifying a weed please

Earlier this year I took over a half plot allotment. I was lucky in that it was not abandoned but handed back. The previous tenants had kept it as grass paths and ground level beds. It was all ready for normal allotment growing. Unluckily, I took it over just at a busy point and right at the start of the growing season. I made the decision to grow like "normal" for this year, getting to know my patch and then make changes later. I'm experimenting a bit but I will post about that separately.

So obviously I am having to do lots of weeding. Boring, annoying as it's been well tended there's few really annoying weeds. But there is one. And it is one that I don't know (having spent years growing and weeding in what is basically just the next field over).

Any ideas?
So far it's made its way up through the mulch I've put down (admittedly not a very deep mulch) and I'm worried about adding it to my compost.

Edit - photos now sorted

That is sheep sorrel, a quite valuable medicinal herb that takes three years to come into its own.
The roots have shown great promise in treatments of some cancers and it is the main active ingredient of the medicinal tea often referred to as Essiac, also known as the four herb tea in Native American culture.

Redhawk

PS, don't rip that out (unless you want to send it to me :-) )

Yup just sorrel, edible if you like really sour things. otherwise pull it out where it is a pain. It's not the worst weed but pretty common.

Agreed, that looks like sheep sorrel to me as well.  I've had lots of it growing in my garden beds, and eaten plenty of it in salads and other dishes.

Thank you everyone. I'll keep pulling it from beds but also start eating it.
After trying to figure it out from looking on online and failing, I knew folks here would know.