Just as you thought the road works had finished!
The Surrey Highways road works map shows upcoming works on the Leatherhead Road between Downsend School and the Knoll Roundabout. The work is scheduled for the following dates: 8 Sep 22:00 - 13 Sep 05:00.
This is a National Highways event and the reason for the works is given as "Works for Road Purposes" - well that's clear enough!