[mmmkay777]

So we moved in a couple of months ago. We have 4 acres which is being stock fenced tomorrow. Horses were kept on the grass but nothing def for 3 months and also 2 fields I think had been left longer - grass is quite long - 6-8 inches. It's turning a bit brown underneath too. So not sure what to do. I have a topper but too wet and cold to top - think it would rot. So any suggestions. We want sheep on it but is it too long for sheep?? So do I wait for spring then top it?  Thanks a lot for your help.

[Foobar]

I would top it, to say half the height.  Let that rot down, then top again to tidy up before the spring growth starts.
Or shove a load of sheep on it, but it might not have much nutritional value so you may have to supplement them.  If you can get a big load of sheep from a local farmer that would probably be best, and I mean a big load, just for a few days.  They will eat what is good and tread in the rest.  Then you can top to tidy up before spring growth starts.