When the harrow is delivered at the end of the week
Our grass was undergrazed last year (and many years before) so lots of thatch plus piles of dung from cows and ponies (plus some pretty big sheep lumps as well) so we'll start harrowing right away. It's dry here, of course, so if it stays that way we'll be able to get on. If it was wet, we wouldn't take machinery on to the land.
I plan to harrow each paddock once we move stock off it, to break up and spread the dung.
We've bought a spring tine grass harrow - the tines are adjustable so that you can just do the dung or you can give the grass right good going over.