Help me drain this swamp.

If my lawn held anymore water I could have one very large wildlife pond. I have bought a house on a half acre site with lawns laid by previous owners. The ground is heavy clay with about the depth of a spade of topsoil.
Forking and topdressing a garden this size would take forever and doubt if it would make much difference. I have considered digging trenches and shoring the garden to aid drainage but with only 10" - 12" of top soil is this really enough as the trenches couldn't really be much deeper as the water won't drain to them through the clay. Any suggestions more than welcome. I bought a ride on lawnmower last year but have had to sell it for a self propelled mower as the ground is always too soft from rain to take the weight of the mower without leaving damage to the lawn.

 

Not really up on land drainage, never had a place large enough or wet enough for it to cause a problem.
Having said that, is there a low point in the garden that the exess water can drain to.
If you dug trenches as you say they would drain through the clay. Land drains used to be layed in trenches then covered in shingle then top soil, but it all needs somewhere to go.
Who was it that said, "Too thin to plough and too thick to drink"

 

Pete that that should be on my gardening motto thread!

as to your drainage problem chkm8 - Just get a professional in your aerea to sort it. I have had several attempts - sorry people who have previously managed my garden have have had several attempts at drainage, if you have this size of problem just get in experts. If you are going to stay in property you will not regret it.