In reply to alam_kouh:
The bits of the Ridgeway I've ridden are pretty straightforward if it's dry, as mostly hard pack and a bit of gravel, not unlike a towpath.
Different story in the wet, though, as it can get very muddy in places and the chalk can get very slippery.
For what you're describing, I'd run something light and low profile, like my Hutchinson Pythons, and pump them up hard on the tarmac
- and watch out for flints
Post edited at 22:04