Posted: 08/11/2013 at 13:22
I use a fork (dtich the spade on heavy clay - I have lost 4) to break up the soil. A pick axe is also good where needed and then I add materials.
Compost and manure will help as Clueless has said. The frosts do shatter clay. I also add in lots of perlite, bark chippings and grit. Forget sand as that and clay can make concrete in summer! It does improve.
I also tried trenching in scraps of food and garden waste, that attracts worms and they do a lot of backbreaking work for you for that waste!