As Adam has said, Walton Heath is clay above chalk.
The British Geological Survey shows it as an area of "Clay - with silt, sand and gravel... on bedrock of chalk", whilst the Natural Environment Research Council show it as an area with soil texture of "clayey loam".
And before you ask, I'm not a geologist, I just have a couple of useful geology apps on my iPhone which come in handy when referencing vernacular architecture...
A quick pan around these apps to a number of other "heathland" courses, shows them all to essentially be on sand of some description, so WH seems a bit of an anomaly from its subsoil perspective.
Cheers,
James