Waterlogged garden

[poncho]

Our garden back onto a large field with is roughly 6 inches higher than the garden. this causes the garden to fill with water every time it rains..... which is quite often being north of Inverness. below the topsoil is clay.
What should I do to rectify this problem.
There is no vehicular access to the back of the house so no chance of a mechanical digger....................................

 

[masona]

Maybe a french drain or a soakaway, there's a load of info regarding french drain on google.