I don't even know if I've got the right name, but it's the valve/tap/c*ck/whatever in the front garden between the 'big' mains water pipe under the road, and the house.
I spent a while prodding and digging out the cover from the front grass, and then lifted the lid to see if it was visible. It isn't, because the thing has filled up with soil. I suppose it would be a good idea to dig it out, or something, but is there a standard depth for these things? I'm just trying to work out how much time to set aside for the job. My plan is to try to wash it out with a hose, since I can't think of anything that will actually fit down there.
And if I do, is it likely to just fill up again?