It's a lichen of some sort - these do pop up on boggy ground.

:) ok thanks!

One of the many liverwort species.

It's a thalloid bryophyte - hepaticum, I think.
Dgw's right, a kind of liverwort.

Liverwort it is! Apparently this is the lowest form of life on the planet ... and equally difficult to get rid of. I have weed-killed and blow-torched it in a patio area, but decided the best way to remove it, as it spreads freely and seems amblivious to weedkiller and blow torch, is by hand, on hands-and-knees!! I recommend you get rid of it asap to the council tip - in your own compost it may well self-seed quietly waiting until you bring it out again.

I get this stuff in the pots on my plant nursery. It's virtually impossible to eliminate

In the garden I ignore it. On pots I remove it. Paint the leaves with Vinegar on seed trays (be careful not to get that on the plants you want though).

ok cool, thanks for all your help-Avkg47 to the council tip it is! I've not got much of it and will be changing all the soil so hopefully it wont reoccur.

It comes from spores in the air, though, so it will keep coming back--usually only a nuisance in pots and seed trays.

Yes the conditions need to be really damp for it to thrive

And it has as much right to exist as any of the other inhabitants of this planet.

It certainly has that right but one can get just a little cheesed off with it when it is swamping 2500 pots!

:^)

I know all about that, it does mine too, but out in the garden................