3 Hills on the A40

I've noticed this for about the last year and a half--When driving to or from London on the A40, there are these 3 hills that appear to be some sort of park or rambling area...it's right near the M4 junction i think...on the right when you're coming in to london, on the left when going back to Brum.

Does anyone know what they are?  My wife said she heard it was built with the Wembley rubble.  Any truth to it?

Yep--your wife is correct. Here's some more info about them:

http://news.bbc.co.uk/1/hi/magazine/7310211.stm

We pass by them every time we come out to see my in-laws.